diff --git a/Makefile b/Makefile
index e9cebb7a..fc4f3bfb 100644
--- a/Makefile
+++ b/Makefile
@@ -144,7 +144,7 @@ mongoose.c: Makefile $(wildcard src/*) $(wildcard mip/*.c)
 	(cat src/license.h; echo; echo '#include "mongoose.h"' ; (for F in src/*.c mip/*.c ; do echo; echo '#ifdef MG_ENABLE_LINES'; echo "#line 1 \"$$F\""; echo '#endif'; cat $$F | sed -e 's,#include ".*,,'; done))> $@
 
 mongoose.h: $(HDRS) Makefile
-	(cat src/license.h; echo; echo '#ifndef MONGOOSE_H'; echo '#define MONGOOSE_H'; echo; cat src/version.h ; echo; echo '#ifdef __cplusplus'; echo 'extern "C" {'; echo '#endif'; cat src/arch.h src/arch_*.h src/config.h src/str.h src/fmt.h src/log.h src/timer.h src/fs.h src/util.h src/url.h src/iobuf.h src/base64.h src/md5.h src/sha1.h src/event.h src/net.h src/http.h src/ssi.h src/tls.h src/tls_mbed.h src/tls_openssl.h src/ws.h src/sntp.h src/mqtt.h src/dns.h src/json.h src/rpc.h mip/mip.h mip/driver_*.h | sed -e '/keep/! s,#include ".*,,' -e 's,^#pragma once,,'; echo; echo '#ifdef __cplusplus'; echo '}'; echo '#endif'; echo '#endif  // MONGOOSE_H')> $@
+	(cat src/license.h; echo; echo '#ifndef MONGOOSE_H'; echo '#define MONGOOSE_H'; echo; cat src/version.h ; echo; echo '#ifdef __cplusplus'; echo 'extern "C" {'; echo '#endif'; cat src/arch.h src/arch_*.h src/net_*.h src/config.h src/str.h src/fmt.h src/log.h src/timer.h src/fs.h src/util.h src/url.h src/iobuf.h src/base64.h src/md5.h src/sha1.h src/event.h src/net.h src/http.h src/ssi.h src/tls.h src/tls_mbed.h src/tls_openssl.h src/ws.h src/sntp.h src/mqtt.h src/dns.h src/json.h src/rpc.h mip/mip.h mip/driver_*.h | sed -e '/keep/! s,#include ".*,,' -e 's,^#pragma once,,'; echo; echo '#ifdef __cplusplus'; echo '}'; echo '#endif'; echo '#endif  // MONGOOSE_H')> $@
 
 clean:
 	rm -rf $(PROG) *.exe *.o *.dSYM *_test* ut fuzzer *.gcov *.gcno *.gcda *.obj *.exe *.ilk *.pdb slow-unit* _CL_* infer-out data.txt crash-* test/packed_fs.c pack
diff --git a/docs/README.md b/docs/README.md
index c1da54f1..0ab37b19 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -267,20 +267,22 @@ files to the application's source tree. The `mongoose.c` and `mongoose.h` files
 are actually an amalgamation - non-amalgamated sources can be found at
 https://github.com/cesanta/mongoose/tree/master/src
 
-Mongoose has two types of build constants (preprocessor definitions) that
-affect the build: a target architecture, and tunables. In order to set the
-option during build time, use the `-D OPTION` compiler flag:
+Mongoose has 3 types of build constants (preprocessor definitions) that affect
+the build: a target architecture/OS, target network stack, and tunables.  In
+order to set the option during build time, use the `-D OPTION` compiler flag:
 
 ```sh
-$ cc app0.c mongoose.c                                        # Use defaults!
-$ cc app1.c mongoose.c -D MG_ENABLE_IPV6=1                    # Build with IPv6 enabled
-$ cc app2.c mongoose.c -D MG_ARCH=MG_ARCH_FREERTOS_LWIP       # Set architecture
-$ cc app3.c mongoose.c -D MG_ENABLE_SSI=0 -D MG_IO_SIZE=8192  # Multiple options
+$ cc app.c mongoose.c                           # Use defaults!
+$ cc app.c mongoose.c -D MG_ENABLE_IPV6=1       # Build with IPv6 enabled
+$ cc app.c mongoose.c -D MG_ARCH=MG_ARCH_RTX    # Set architecture
+$ cc app.c mongoose.c -D MG_ENABLE_SSI=0 -D MG_IO_SIZE=8192  # Multiple options
 ```
 
-The list of supported architectures is defined in the [arch.h](https://github.com/cesanta/mongoose/blob/master/src/arch.h)
-header file. Normally, there is no need to explicitly specify the architecture.
-The architecture is guessed during the build, so setting it is not usually required.
+The list of supported architectures is defined in the
+[arch.h](https://github.com/cesanta/mongoose/blob/master/src/arch.h) header
+file. Normally, there is no need to explicitly specify the architecture.  The
+architecture is guessed during the build, so setting it is not usually
+required.
 
 | Name | Description |
 | ---- | ----------- |
@@ -288,17 +290,26 @@ The architecture is guessed during the build, so setting it is not usually requi
 |MG_ARCH_WIN32 | Windows systems |
 |MG_ARCH_ESP32 | Espressif's ESP32 |
 |MG_ARCH_ESP8266 | Espressif's ESP8266 |
-|MG_ARCH_FREERTOS_LWIP | All systems with FreeRTOS kernel and LwIP IP stack |
-|MG_ARCH_FREERTOS_TCP | All systems with FreeRTOS kernel and FreeRTOS-Plus-TCP IP stack |
+|MG_ARCH_FREERTOS | All systems with FreeRTOS kernel|
 |MG_ARCH_AZURERTOS | Microsoft Azure RTOS |
-|MG_ARCH_RTX_LWIP | Keil RTX with LWIP TCP/IP stack |
-|MG_ARCH_RTX | Keil RTX with MDK TCP/IP stack |
+|MG_ARCH_RTX | Keil RTX  |
 |MG_ARCH_ZEPHYR | Zephyr RTOS |
 |MG_ARCH_TIRTOS | TI RTOS |
 |MG_ARCH_RP2040 | RP2040 SDK |
 |MG_ARCH_NEWLIB | Bare ARM GCC |
 |MG_ARCH_CUSTOM | A custom architecture, discussed in the next section |
 
+The network stack constants are listed below. Note that if a network stack
+is not specified, then it is assumed that the target architecture supports
+standard BSD socket API.
+
+| Name | Default  | Description |
+| ---- | -------- | ----------- |
+|MG_ENABLE_LWIP | 0 | lwIP network stack |
+|MG_ENABLE_FREERTOS_TCP | 0 | Amazon FreeRTOS-Plus-TCP network stack |
+|MG_ENABLE_RL | 0 | Keil MDK network stack |
+|MG_ENABLE_MIP | 0 | Built-in Mongoose network stack |
+
 The other class of build constants is defined in
 [src/config.h](https://github.com/cesanta/mongoose/blob/master/src/config.h)
 together with their default values. These are tunables that include/exclude
diff --git a/examples/stm32/nucleo-f429zi-baremetal/mcu.h b/examples/stm32/nucleo-f429zi-baremetal/mcu.h
index d4f23d3d..3b226b7e 100644
--- a/examples/stm32/nucleo-f429zi-baremetal/mcu.h
+++ b/examples/stm32/nucleo-f429zi-baremetal/mcu.h
@@ -22,7 +22,7 @@ enum { APB1_PRE = 5 /* AHB clock / 4 */, APB2_PRE = 4 /* AHB clock / 2 */ };
 enum { PLL_HSI = 16, PLL_M = 8, PLL_N = 180, PLL_P = 2 };  // Run at 180 Mhz
 //#define PLL_FREQ PLL_HSI
 #define PLL_FREQ (PLL_HSI * PLL_N / PLL_M / PLL_P)
-#define FLASH_LATENCY 5 
+#define FLASH_LATENCY 5
 #define FREQ (PLL_FREQ * 1000000)
 
 static inline void spin(volatile uint32_t count) {
@@ -175,9 +175,10 @@ static inline void uart_init(struct uart *uart, unsigned long baud) {
 
   gpio_init(tx, GPIO_MODE_AF, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_HIGH, 0, af);
   gpio_init(rx, GPIO_MODE_AF, GPIO_OTYPE_PUSH_PULL, GPIO_SPEED_HIGH, 0, af);
-  uart->CR1 = 0;                          // Disable this UART
-  uart->BRR = FREQ / 4 / baud;      // Baud rate x16 (with 4dp), "4" is APBx prescaler, different from APBx_PRE
-                                    // TODO(): make this configurable ?
+  uart->CR1 = 0;                       // Disable this UART
+  uart->BRR = FREQ / APB2_PRE / baud;  // Baud rate x16 (with 4dp), "4" is APBx
+                                       // prescaler, different from APBx_PRE
+                                       // TODO(): make this configurable ?
   uart->CR1 |= BIT(13) | BIT(2) | BIT(3);  // Set UE, RE, TE
 }
 static inline void uart_write_byte(struct uart *uart, uint8_t byte) {
@@ -194,12 +195,13 @@ static inline uint8_t uart_read_byte(struct uart *uart) {
   return (uint8_t) (uart->DR & 255);
 }
 
-static inline void clock_init(void) {  // Set clock frequency
+static inline void clock_init(void) {                 // Set clock frequency
   SCB->CPACR |= ((3UL << 10 * 2) | (3UL << 11 * 2));  // Enable FPU
-  asm ("DSB");
-  asm ("ISB");
-  FLASH->ACR |= FLASH_LATENCY | BIT(8) | BIT(9);    // Flash latency, prefetch, Icache, Dcache
-  RCC->PLLCFGR &= ~((BIT(17) - 1));                 // Clear PLL multipliers
+  asm("DSB");
+  asm("ISB");
+  FLASH->ACR |= FLASH_LATENCY | BIT(8) |
+                BIT(9);              // Flash latency, prefetch, Icache, Dcache
+  RCC->PLLCFGR &= ~((BIT(17) - 1));  // Clear PLL multipliers
   RCC->PLLCFGR |= (((PLL_P - 2) / 2) & 3) << 16;    // Set PLL_P
   RCC->PLLCFGR |= PLL_M | (PLL_N << 6);             // Set PLL_M and PLL_N
   RCC->CR |= BIT(24);                               // Enable PLL
diff --git a/examples/stm32/stm32-freertos-tcp/Makefile b/examples/stm32/stm32-freertos-tcp/Makefile
index b5a77dbe..f91199f4 100644
--- a/examples/stm32/stm32-freertos-tcp/Makefile
+++ b/examples/stm32/stm32-freertos-tcp/Makefile
@@ -6,7 +6,7 @@ DOCKER ?= docker run --rm -v $(PROJECT_ROOT_PATH):$(PROJECT_ROOT_PATH) -w $(CURD
 FREERTOS_KERNEL_PATH ?= $(PROJECT_ROOT_PATH)/test/freertos-kernel
 FREERTOS_PLUS_TCP_PATH ?= $(PROJECT_ROOT_PATH)/test/freertos-tcp
 
-MONGOOSE_FLAGS = -DMG_ARCH=MG_ARCH_FREERTOS_TCP
+MONGOOSE_FLAGS = -DMG_ARCH=MG_ARCH_FREERTOS -DMG_ENABLE_FREERTOS_TCP -DMG_ENABLE_FILE=0
 MCU_FLAGS = -mcpu=cortex-m7 -mthumb -mfloat-abi=softfp -mfpu=vfpv4
 #-mcpu=cortex-m7 -mthumb -mfpu=fpv5-sp-d16 -mfloat-abi=hard
 
diff --git a/mip/driver_stm32.c b/mip/driver_stm32.c
index 6cb962bf..03cea143 100644
--- a/mip/driver_stm32.c
+++ b/mip/driver_stm32.c
@@ -14,8 +14,10 @@ struct stm32_eth {
       DMAMFBOCR, DMARSWTR, RESERVED10[8], DMACHTDR, DMACHRDR, DMACHTBAR,
       DMACHRBAR;
 };
+#undef ETH
 #define ETH ((struct stm32_eth *) (uintptr_t) 0x40028000)
 
+#undef BIT
 #define BIT(x) ((uint32_t) 1 << (x))
 #define ETH_PKT_SIZE 1540  // Max frame size
 #define ETH_DESC_CNT 4     // Descriptors count
@@ -29,15 +31,11 @@ static void (*s_rx)(void *, size_t, void *);         // Recv callback
 static void *s_rxdata;                               // Recv callback data
 enum { PHY_ADDR = 0, PHY_BCR = 0, PHY_BSR = 1 };     // PHY constants
 
-static inline void spin(volatile uint32_t count) {
-  while (count--) (void) 0;
-}
-
 static uint32_t eth_read_phy(uint8_t addr, uint8_t reg) {
   ETH->MACMIIAR &= (7 << 2);
   ETH->MACMIIAR |= ((uint32_t) addr << 11) | ((uint32_t) reg << 6);
   ETH->MACMIIAR |= BIT(0);
-  while (ETH->MACMIIAR & BIT(0)) spin(1);
+  while (ETH->MACMIIAR & BIT(0)) (void) 0;
   return ETH->MACMIIDR;
 }
 
@@ -46,29 +44,29 @@ static void eth_write_phy(uint8_t addr, uint8_t reg, uint32_t val) {
   ETH->MACMIIAR &= (7 << 2);
   ETH->MACMIIAR |= ((uint32_t) addr << 11) | ((uint32_t) reg << 6) | BIT(1);
   ETH->MACMIIAR |= BIT(0);
-  while (ETH->MACMIIAR & BIT(0)) spin(1);
+  while (ETH->MACMIIAR & BIT(0)) (void) 0;
 }
 
 static uint32_t get_hclk(void) {
   struct rcc {
     volatile uint32_t CR, PLLCFGR, CFGR;
-  } *RCC = (struct rcc *) 0x40023800;
+  } *rcc = (struct rcc *) 0x40023800;
   uint32_t clk = 0, hsi = 16000000 /* 16 MHz */, hse = 8000000 /* 8MHz */;
 
-  if (RCC->CFGR & (1 << 2)) {
+  if (rcc->CFGR & (1 << 2)) {
     clk = hse;
-  } else if (RCC->CFGR & (1 << 3)) {
+  } else if (rcc->CFGR & (1 << 3)) {
     uint32_t vco, m, n, p;
-    m = (RCC->PLLCFGR & (0x3f << 0)) >> 0;
-    n = (RCC->PLLCFGR & (0x1ff << 6)) >> 6;
-    p = (((RCC->PLLCFGR & (3 << 16)) >> 16) + 1) * 2;
-    clk = (RCC->PLLCFGR & (1 << 22)) ? hse : hsi;
+    m = (rcc->PLLCFGR & (0x3f << 0)) >> 0;
+    n = (rcc->PLLCFGR & (0x1ff << 6)) >> 6;
+    p = (((rcc->PLLCFGR & (3 << 16)) >> 16) + 1) * 2;
+    clk = (rcc->PLLCFGR & (1 << 22)) ? hse : hsi;
     vco = (uint32_t) ((uint64_t) clk * n / m);
     clk = vco / p;
   } else {
     clk = hsi;
   }
-  uint32_t hpre = (RCC->CFGR & (15 << 4)) >> 4;
+  uint32_t hpre = (rcc->CFGR & (15 << 4)) >> 4;
   if (hpre < 8) return clk;
 
   uint8_t ahbptab[8] = {1, 2, 3, 4, 6, 7, 8, 9};  // log2(div)
@@ -121,12 +119,12 @@ static bool mip_driver_stm32_init(uint8_t *mac, void *userdata) {
         (uint32_t) (uintptr_t) s_txdesc[(i + 1) % ETH_DESC_CNT];  // Chain
   }
 
-  ETH->DMABMR |= BIT(0);                        // Software reset
-  while ((ETH->DMABMR & BIT(0)) != 0) spin(1);  // Wait until done
+  ETH->DMABMR |= BIT(0);                         // Software reset
+  while ((ETH->DMABMR & BIT(0)) != 0) (void) 0;  // Wait until done
 
   // Set MDC clock divider. If user told us the value, use it. Otherwise, guess
   int cr = (d == NULL || d->mdc_cr < 0) ? guess_mdc_cr() : d->mdc_cr;
-  ETH->MACMIIAR = ((uint32_t)cr & 7) << 2;
+  ETH->MACMIIAR = ((uint32_t) cr & 7) << 2;
 
   // NOTE(cpq): we do not use extended descriptor bit 7, and do not use
   // hardware checksum. Therefore, descriptor size is 4, not 8
diff --git a/mip/mip.c b/mip/mip.c
index eb6a2540..2e83c230 100644
--- a/mip/mip.c
+++ b/mip/mip.c
@@ -628,7 +628,7 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
 
     MG_DEBUG(("%lu SEQ %x -> %x", c->id, mg_htonl(pkt->tcp->seq), s->ack));
     s->ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len);
-#if 1
+#if 0
     // Send ACK immediately
     MG_DEBUG(("  imm ACK", c->id, mg_htonl(pkt->tcp->seq), s->ack));
     tx_tcp((struct mip_if *) c->mgr->priv, c->rem.ip, TH_ACK, c->loc.port,
diff --git a/mongoose.c b/mongoose.c
index c2ee5a01..f74bcfbc 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -3529,7 +3529,7 @@ void mg_mgr_free(struct mg_mgr *mgr) {
   mgr->timers = NULL;  // Important. Next call to poll won't touch timers
   for (c = mgr->conns; c != NULL; c = c->next) c->is_closing = 1;
   mg_mgr_poll(mgr, 0);
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
   FreeRTOS_DeleteSocketSet(mgr->ss);
 #endif
   MG_DEBUG(("All connections closed"));
@@ -3550,7 +3550,7 @@ void mg_mgr_init(struct mg_mgr *mgr) {
   // clang-format off
   { WSADATA data; WSAStartup(MAKEWORD(2, 2), &data); }
   // clang-format on
-#elif MG_ARCH == MG_ARCH_FREERTOS_TCP
+#elif MG_ENABLE_FREERTOS_TCP
   mgr->ss = FreeRTOS_CreateSocketSet();
 #elif defined(__unix) || defined(__unix__) || defined(__APPLE__)
   // Ignore SIGPIPE signal, so if client cancels the request, it
@@ -4100,7 +4100,7 @@ long mg_io_send(struct mg_connection *c, const void *buf, size_t len) {
   } else {
     n = send(FD(c), (char *) buf, len, MSG_NONBLOCKING);
 #if MG_ARCH == MG_ARCH_RTX
-    if (n == BSD_EWOULDBLOCK) return MG_IO_WAIT;
+    if (n == EWOULDBLOCK) return MG_IO_WAIT;
 #endif
   }
   if (n < 0 && mg_sock_would_block()) return MG_IO_WAIT;
@@ -4130,11 +4130,11 @@ static void mg_set_non_blocking_mode(MG_SOCKET_TYPE fd) {
 #elif MG_ARCH == MG_ARCH_RTX
   unsigned long on = 1;
   ioctlsocket(fd, FIONBIO, &on);
-#elif MG_ARCH == MG_ARCH_FREERTOS_TCP
+#elif MG_ENABLE_FREERTOS_TCP
   const BaseType_t off = 0;
   if (setsockopt(fd, 0, FREERTOS_SO_RCVTIMEO, &off, sizeof(off)) != 0) (void) 0;
   if (setsockopt(fd, 0, FREERTOS_SO_SNDTIMEO, &off, sizeof(off)) != 0) (void) 0;
-#elif MG_ARCH == MG_ARCH_FREERTOS_LWIP || MG_ARCH == MG_ARCH_RTX_LWIP
+#elif MG_ENABLE_LWIP
   lwip_fcntl(fd, F_SETFL, O_NONBLOCK);
 #elif MG_ARCH == MG_ARCH_AZURERTOS
   fcntl(fd, F_SETFL, O_NONBLOCK);
@@ -4262,7 +4262,7 @@ static void close_conn(struct mg_connection *c) {
     epoll_ctl(c->mgr->epoll_fd, EPOLL_CTL_DEL, FD(c), NULL);
 #endif
     closesocket(FD(c));
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
     FreeRTOS_FD_CLR(c->fd, c->mgr->ss, eSELECT_ALL);
 #endif
   }
@@ -4284,7 +4284,7 @@ static void connect_conn(struct mg_connection *c) {
 }
 
 static void setsockopts(struct mg_connection *c) {
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP || MG_ARCH == MG_ARCH_AZURERTOS || \
+#if MG_ENABLE_FREERTOS_TCP || MG_ARCH == MG_ARCH_AZURERTOS || \
     MG_ARCH == MG_ARCH_TIRTOS
   (void) c;
 #else
@@ -4312,7 +4312,8 @@ void mg_connect_resolved(struct mg_connection *c) {
 #if MG_ARCH == MG_ARCH_TIRTOS
     union usa usa;  // TI-RTOS NDK requires binding to receive on UDP sockets
     socklen_t slen = tousa(&c->loc, &usa);
-    if (bind(c->fd, &usa.sa, slen) != 0) MG_ERROR(("bind: %d", MG_SOCKET_ERRNO));
+    if (bind(c->fd, &usa.sa, slen) != 0)
+      MG_ERROR(("bind: %d", MG_SOCKET_ERRNO));
 #endif
     mg_call(c, MG_EV_RESOLVE, NULL);
     mg_call(c, MG_EV_CONNECT, NULL);
@@ -4336,7 +4337,8 @@ void mg_connect_resolved(struct mg_connection *c) {
   (void) rc;
 }
 
-static MG_SOCKET_TYPE raccept(MG_SOCKET_TYPE sock, union usa *usa, socklen_t len) {
+static MG_SOCKET_TYPE raccept(MG_SOCKET_TYPE sock, union usa *usa,
+                              socklen_t len) {
   MG_SOCKET_TYPE s = MG_INVALID_SOCKET;
   do {
     memset(usa, 0, sizeof(*usa));
@@ -4358,8 +4360,8 @@ static void accept_conn(struct mg_mgr *mgr, struct mg_connection *lsn) {
     if (MG_SOCKET_ERRNO != EAGAIN)
 #endif
       MG_ERROR(("%lu accept failed, errno %d", lsn->id, MG_SOCKET_ERRNO));
-#if (MG_ARCH != MG_ARCH_WIN32) && (MG_ARCH != MG_ARCH_FREERTOS_TCP) && \
-    (MG_ARCH != MG_ARCH_TIRTOS) && !(MG_ENABLE_POLL)
+#if (MG_ARCH != MG_ARCH_WIN32) && !MG_ENABLE_FREERTOS_TCP && \
+    (MG_ARCH != MG_ARCH_TIRTOS) && !MG_ENABLE_POLL
   } else if ((long) fd >= FD_SETSIZE) {
     MG_ERROR(("%ld > %ld", (long) fd, (long) FD_SETSIZE));
     closesocket(fd);
@@ -4463,7 +4465,7 @@ static bool skip_iotest(const struct mg_connection *c) {
 }
 
 static void mg_iotest(struct mg_mgr *mgr, int ms) {
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
   struct mg_connection *c;
   for (c = mgr->conns; c != NULL; c = c->next) {
     c->is_readable = c->is_writable = 0;
@@ -4475,8 +4477,8 @@ static void mg_iotest(struct mg_mgr *mgr, int ms) {
   FreeRTOS_select(mgr->ss, pdMS_TO_TICKS(ms));
   for (c = mgr->conns; c != NULL; c = c->next) {
     EventBits_t bits = FreeRTOS_FD_ISSET(c->fd, mgr->ss);
-    c->is_readable = bits & (eSELECT_READ | eSELECT_EXCEPT) ? 1 : 0;
-    c->is_writable = bits & eSELECT_WRITE ? 1 : 0;
+    c->is_readable = bits & (eSELECT_READ | eSELECT_EXCEPT) ? 1U : 0;
+    c->is_writable = bits & eSELECT_WRITE ? 1U : 0;
     FreeRTOS_FD_CLR(c->fd, mgr->ss,
                     eSELECT_READ | eSELECT_EXCEPT | eSELECT_WRITE);
   }
@@ -5598,9 +5600,7 @@ uint64_t mg_millis(void) {
   return time_us_64() / 1000;
 #elif MG_ARCH == MG_ARCH_ESP32
   return esp_timer_get_time() / 1000;
-#elif MG_ARCH == MG_ARCH_ESP8266
-  return xTaskGetTickCount() * portTICK_PERIOD_MS;
-#elif MG_ARCH == MG_ARCH_FREERTOS_TCP || MG_ARCH == MG_ARCH_FREERTOS_LWIP
+#elif MG_ARCH == MG_ARCH_ESP8266 || MG_ARCH == MG_ARCH_FREERTOS
   return xTaskGetTickCount() * portTICK_PERIOD_MS;
 #elif MG_ARCH == MG_ARCH_AZURERTOS
   return tx_time_get() * (1000 /* MS per SEC */ / TX_TIMER_TICKS_PER_SECOND);
@@ -5999,8 +5999,10 @@ struct stm32_eth {
       DMAMFBOCR, DMARSWTR, RESERVED10[8], DMACHTDR, DMACHRDR, DMACHTBAR,
       DMACHRBAR;
 };
+#undef ETH
 #define ETH ((struct stm32_eth *) (uintptr_t) 0x40028000)
 
+#undef BIT
 #define BIT(x) ((uint32_t) 1 << (x))
 #define ETH_PKT_SIZE 1540  // Max frame size
 #define ETH_DESC_CNT 4     // Descriptors count
@@ -6014,15 +6016,11 @@ static void (*s_rx)(void *, size_t, void *);         // Recv callback
 static void *s_rxdata;                               // Recv callback data
 enum { PHY_ADDR = 0, PHY_BCR = 0, PHY_BSR = 1 };     // PHY constants
 
-static inline void spin(volatile uint32_t count) {
-  while (count--) (void) 0;
-}
-
 static uint32_t eth_read_phy(uint8_t addr, uint8_t reg) {
   ETH->MACMIIAR &= (7 << 2);
   ETH->MACMIIAR |= ((uint32_t) addr << 11) | ((uint32_t) reg << 6);
   ETH->MACMIIAR |= BIT(0);
-  while (ETH->MACMIIAR & BIT(0)) spin(1);
+  while (ETH->MACMIIAR & BIT(0)) (void) 0;
   return ETH->MACMIIDR;
 }
 
@@ -6031,29 +6029,29 @@ static void eth_write_phy(uint8_t addr, uint8_t reg, uint32_t val) {
   ETH->MACMIIAR &= (7 << 2);
   ETH->MACMIIAR |= ((uint32_t) addr << 11) | ((uint32_t) reg << 6) | BIT(1);
   ETH->MACMIIAR |= BIT(0);
-  while (ETH->MACMIIAR & BIT(0)) spin(1);
+  while (ETH->MACMIIAR & BIT(0)) (void) 0;
 }
 
 static uint32_t get_hclk(void) {
   struct rcc {
     volatile uint32_t CR, PLLCFGR, CFGR;
-  } *RCC = (struct rcc *) 0x40023800;
+  } *rcc = (struct rcc *) 0x40023800;
   uint32_t clk = 0, hsi = 16000000 /* 16 MHz */, hse = 8000000 /* 8MHz */;
 
-  if (RCC->CFGR & (1 << 2)) {
+  if (rcc->CFGR & (1 << 2)) {
     clk = hse;
-  } else if (RCC->CFGR & (1 << 3)) {
+  } else if (rcc->CFGR & (1 << 3)) {
     uint32_t vco, m, n, p;
-    m = (RCC->PLLCFGR & (0x3f << 0)) >> 0;
-    n = (RCC->PLLCFGR & (0x1ff << 6)) >> 6;
-    p = (((RCC->PLLCFGR & (3 << 16)) >> 16) + 1) * 2;
-    clk = (RCC->PLLCFGR & (1 << 22)) ? hse : hsi;
+    m = (rcc->PLLCFGR & (0x3f << 0)) >> 0;
+    n = (rcc->PLLCFGR & (0x1ff << 6)) >> 6;
+    p = (((rcc->PLLCFGR & (3 << 16)) >> 16) + 1) * 2;
+    clk = (rcc->PLLCFGR & (1 << 22)) ? hse : hsi;
     vco = (uint32_t) ((uint64_t) clk * n / m);
     clk = vco / p;
   } else {
     clk = hsi;
   }
-  uint32_t hpre = (RCC->CFGR & (15 << 4)) >> 4;
+  uint32_t hpre = (rcc->CFGR & (15 << 4)) >> 4;
   if (hpre < 8) return clk;
 
   uint8_t ahbptab[8] = {1, 2, 3, 4, 6, 7, 8, 9};  // log2(div)
@@ -6106,12 +6104,12 @@ static bool mip_driver_stm32_init(uint8_t *mac, void *userdata) {
         (uint32_t) (uintptr_t) s_txdesc[(i + 1) % ETH_DESC_CNT];  // Chain
   }
 
-  ETH->DMABMR |= BIT(0);                        // Software reset
-  while ((ETH->DMABMR & BIT(0)) != 0) spin(1);  // Wait until done
+  ETH->DMABMR |= BIT(0);                         // Software reset
+  while ((ETH->DMABMR & BIT(0)) != 0) (void) 0;  // Wait until done
 
   // Set MDC clock divider. If user told us the value, use it. Otherwise, guess
   int cr = (d == NULL || d->mdc_cr < 0) ? guess_mdc_cr() : d->mdc_cr;
-  ETH->MACMIIAR = ((uint32_t)cr & 7) << 2;
+  ETH->MACMIIAR = ((uint32_t) cr & 7) << 2;
 
   // NOTE(cpq): we do not use extended descriptor bit 7, and do not use
   // hardware checksum. Therefore, descriptor size is 4, not 8
@@ -6918,7 +6916,7 @@ static void read_conn(struct mg_connection *c, struct pkt *pkt) {
 
     MG_DEBUG(("%lu SEQ %x -> %x", c->id, mg_htonl(pkt->tcp->seq), s->ack));
     s->ack = (uint32_t) (mg_htonl(pkt->tcp->seq) + pkt->pay.len);
-#if 1
+#if 0
     // Send ACK immediately
     MG_DEBUG(("  imm ACK", c->id, mg_htonl(pkt->tcp->seq), s->ack));
     tx_tcp((struct mip_if *) c->mgr->priv, c->rem.ip, TH_ACK, c->loc.port,
diff --git a/mongoose.h b/mongoose.h
index c30b5301..c32b3dfc 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -27,20 +27,18 @@ extern "C" {
 #endif
 
 
-#define MG_ARCH_CUSTOM 0
-#define MG_ARCH_UNIX 1
-#define MG_ARCH_WIN32 2
-#define MG_ARCH_ESP32 3
-#define MG_ARCH_ESP8266 4
-#define MG_ARCH_FREERTOS_TCP 5
-#define MG_ARCH_FREERTOS_LWIP 6
-#define MG_ARCH_AZURERTOS 7
-#define MG_ARCH_RTX_LWIP 8
-#define MG_ARCH_ZEPHYR 9
-#define MG_ARCH_NEWLIB 10
-#define MG_ARCH_RTX 11
-#define MG_ARCH_TIRTOS 12
-#define MG_ARCH_RP2040 13
+#define MG_ARCH_CUSTOM 0     // User creates its own mongoose_custom.h
+#define MG_ARCH_UNIX 1       // Linux, BSD, Mac, ...
+#define MG_ARCH_WIN32 2      // Windows
+#define MG_ARCH_ESP32 3      // ESP32
+#define MG_ARCH_ESP8266 4    // ESP8266
+#define MG_ARCH_FREERTOS 5   // FreeRTOS
+#define MG_ARCH_AZURERTOS 6  // MS Azure RTOS
+#define MG_ARCH_ZEPHYR 7     // Zephyr RTOS
+#define MG_ARCH_NEWLIB 8     // Bare metal ARM
+#define MG_ARCH_RTX 9        // Keil MDK RTX
+#define MG_ARCH_TIRTOS 10    // Texas Semi TI-RTOS
+#define MG_ARCH_RP2040 11    // Raspberry Pi RP2040
 
 #if !defined(MG_ARCH)
 #if defined(__unix__) || defined(__APPLE__)
@@ -54,7 +52,8 @@ extern "C" {
 #elif defined(ESP_PLATFORM)
 #define MG_ARCH MG_ARCH_ESP32
 #elif defined(FREERTOS_IP_H)
-#define MG_ARCH MG_ARCH_FREERTOS_TCP
+#define MG_ARCH MG_ARCH_FREERTOS
+#define MG_ENABLE_FREERTOS_TCP 1
 #elif defined(AZURE_RTOS_THREADX)
 #define MG_ARCH MG_ARCH_AZURERTOS
 #elif defined(PICO_TARGET_NAME)
@@ -71,7 +70,9 @@ extern "C" {
 #endif
 
 // http://esr.ibiblio.org/?p=5095
-#define MG_BIG_ENDIAN (*(uint16_t *)"\0\xff" < 0x100)
+#define MG_BIG_ENDIAN (*(uint16_t *) "\0\xff" < 0x100)
+
+
 
 
 
@@ -162,9 +163,10 @@ extern "C" {
 #endif
 
 
-#if MG_ARCH == MG_ARCH_FREERTOS_LWIP
+#if MG_ARCH == MG_ARCH_FREERTOS
 
 #include <ctype.h>
+// #include <errno.h> // Cannot include errno - might conflict with lwip!
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -172,137 +174,32 @@ extern "C" {
 #include <stdio.h>
 #include <string.h>
 
-#if defined(__GNUC__)
-#include <sys/stat.h>
-#include <sys/time.h>
-#else
-struct timeval {
-  time_t tv_sec;
-  long tv_usec;
-};
-#endif
-
 #include <FreeRTOS.h>
 #include <task.h>
 
-#include <lwip/sockets.h>
-
-#if LWIP_SOCKET != 1
-// Sockets support disabled in LWIP by default
-#error Set LWIP_SOCKET variable to 1 (in lwipopts.h)
-#endif
-
-// Re-route calloc/free to the FreeRTOS's functions, don't use stdlib
-static inline void *mg_calloc(int cnt, size_t size) {
-  void *p = pvPortMalloc(cnt * size);
-  if (p != NULL) memset(p, 0, size * cnt);
-  return p;
-}
-#define calloc(a, b) mg_calloc((a), (b))
-#define free(a) vPortFree(a)
-#define malloc(a) pvPortMalloc(a)
-#define strdup(s) ((char *) mg_strdup(mg_str(s)).ptr)
-#define mkdir(a, b) (-1)
-
 #ifndef MG_IO_SIZE
 #define MG_IO_SIZE 512
 #endif
 
-#endif  // MG_ARCH == MG_ARCH_FREERTOS_LWIP
-
-
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
-
-#include <ctype.h>
-#include <errno.h>
-#include <limits.h>
-#include <stdarg.h>
-#include <stdbool.h>
-#include <stddef.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/stat.h>
-#include <time.h>
-
-#include <FreeRTOS.h>
-#include <list.h>
-#include <task.h>
-
-#include <FreeRTOS_IP.h>
-#include <FreeRTOS_Sockets.h>
-
-#define MG_SOCKET_TYPE Socket_t
-#define MG_INVALID_SOCKET FREERTOS_INVALID_SOCKET
-
-// Why FreeRTOS-TCP did not implement a clean BSD API, but its own thing
-// with FreeRTOS_ prefix, is beyond me
-#define IPPROTO_TCP FREERTOS_IPPROTO_TCP
-#define IPPROTO_UDP FREERTOS_IPPROTO_UDP
-#define AF_INET FREERTOS_AF_INET
-#define SOCK_STREAM FREERTOS_SOCK_STREAM
-#define SOCK_DGRAM FREERTOS_SOCK_DGRAM
-#define SO_BROADCAST 0
-#define SO_ERROR 0
-#define SOL_SOCKET 0
-#define SO_REUSEADDR 0
-#define sockaddr_in freertos_sockaddr
-#define sockaddr freertos_sockaddr
-#define accept(a, b, c) FreeRTOS_accept((a), (b), (c))
-#define connect(a, b, c) FreeRTOS_connect((a), (b), (c))
-#define bind(a, b, c) FreeRTOS_bind((a), (b), (c))
-#define listen(a, b) FreeRTOS_listen((a), (b))
-#define socket(a, b, c) FreeRTOS_socket((a), (b), (c))
-#define send(a, b, c, d) FreeRTOS_send((a), (b), (c), (d))
-#define recv(a, b, c, d) FreeRTOS_recv((a), (b), (c), (d))
-#define setsockopt(a, b, c, d, e) FreeRTOS_setsockopt((a), (b), (c), (d), (e))
-#define sendto(a, b, c, d, e, f) FreeRTOS_sendto((a), (b), (c), (d), (e), (f))
-#define recvfrom(a, b, c, d, e, f) \
-  FreeRTOS_recvfrom((a), (b), (c), (d), (e), (f))
-#define closesocket(x) FreeRTOS_closesocket(x)
-#define gethostbyname(x) FreeRTOS_gethostbyname(x)
-#define getsockname(a, b, c) (-1)
-#define getpeername(a, b, c) 0
+#define calloc(a, b) mg_calloc(a, b)
+#define free(a) vPortFree(a)
+#define malloc(a) pvPortMalloc(a)
+#define strdup(s) ((char *) mg_strdup(mg_str(s)).ptr)
 
 // Re-route calloc/free to the FreeRTOS's functions, don't use stdlib
-static inline void *mg_calloc(int cnt, size_t size) {
+static inline void *mg_calloc(size_t cnt, size_t size) {
   void *p = pvPortMalloc(cnt * size);
   if (p != NULL) memset(p, 0, size * cnt);
   return p;
 }
-#define calloc(a, b) mg_calloc((a), (b))
-#define free(a) vPortFree(a)
-#define malloc(a) pvPortMalloc(a)
-#define mkdir(a, b) (-1)
 
-#if !defined(__GNUC__)
-// copied from GCC on ARM; for some reason useconds are signed
-struct timeval {
-  time_t tv_sec;
-  long tv_usec;
-};
-#endif
+#define mkdir(a, b) mg_mkdir(a, b)
+static inline int mg_mkdir(const char *path, mode_t mode) {
+  (void) path, (void) mode;
+  return -1;
+}
 
-#ifndef EINPROGRESS
-#define EINPROGRESS pdFREERTOS_ERRNO_EINPROGRESS
-#endif
-#ifndef EWOULDBLOCK
-#define EWOULDBLOCK pdFREERTOS_ERRNO_EWOULDBLOCK
-#endif
-#ifndef EAGAIN
-#define EAGAIN pdFREERTOS_ERRNO_EAGAIN
-#endif
-#ifndef EINTR
-#define EINTR pdFREERTOS_ERRNO_EINTR
-#endif
-
-// FreeRTOS-TCP uses non-standard semantics for listen() backlog size. It is
-// not a backlog size for pending SYN connections, but a max socket number
-#ifndef MG_SOCK_LISTEN_BACKLOG_SIZE
-#define MG_SOCK_LISTEN_BACKLOG_SIZE 128
-#endif
-
-#endif  // MG_ARCH == MG_ARCH_FREERTOS_TCP
+#endif  // MG_ARCH == MG_ARCH_FREERTOS
 
 
 #if MG_ARCH == MG_ARCH_NEWLIB
@@ -356,60 +253,10 @@ int mkdir(const char *, mode_t);
 #include <string.h>
 #include <time.h>
 
-#include <rl_net.h>
-
-#define MG_ENABLE_CUSTOM_MILLIS 1
-typedef int socklen_t;
-#define closesocket(x) closesocket(x)
-#define mkdir(a, b) (-1)
-#define EWOULDBLOCK BSD_EWOULDBLOCK
-#define EAGAIN BSD_EWOULDBLOCK
-#define EINPROGRESS BSD_EWOULDBLOCK
-#define EINTR BSD_EWOULDBLOCK
-#define ECONNRESET BSD_ECONNRESET
-#define EPIPE BSD_ECONNRESET
-#define TCP_NODELAY SO_KEEPALIVE
-
+#if !defined MG_ENABLE_RL && (!defined(MG_ENABLE_LWIP) || !MG_ENABLE_LWIP)
+#define MG_ENABLE_RL 1
 #endif
 
-
-#if MG_ARCH == MG_ARCH_RTX_LWIP
-
-#include <ctype.h>
-#include <stdarg.h>
-#include <stdbool.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>
-
-#if defined(__GNUC__)
-#include <sys/stat.h>
-#include <sys/time.h>
-#else
-struct timeval {
-  time_t tv_sec;
-  long tv_usec;
-};
-#endif
-
-#include <lwip/sockets.h>
-
-#if LWIP_SOCKET != 1
-// Sockets support disabled in LWIP by default
-#error Set LWIP_SOCKET variable to 1 (in lwipopts.h)
-#endif
-
-#define mkdir(a, b) (-1)
-
-#ifndef MG_IO_SIZE
-#define MG_IO_SIZE 512
-#endif
-
-#ifndef MG_PATH_MAX
-#define MG_PATH_MAX 128
-#endif
-
-
 #endif
 
 
@@ -626,12 +473,129 @@ int sscanf(const char *, const char *, ...);
 #endif
 
 
+#if defined(MG_ENABLE_FREERTOS_TCP) && MG_ENABLE_FREERTOS_TCP
+
+#include <ctype.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <time.h>
+
+#include <FreeRTOS.h>
+#include <list.h>
+#include <task.h>
+
+#include <FreeRTOS_IP.h>
+#include <FreeRTOS_Sockets.h>
+
+#define MG_SOCKET_TYPE Socket_t
+#define MG_INVALID_SOCKET FREERTOS_INVALID_SOCKET
+
+// Why FreeRTOS-TCP did not implement a clean BSD API, but its own thing
+// with FreeRTOS_ prefix, is beyond me
+#define IPPROTO_TCP FREERTOS_IPPROTO_TCP
+#define IPPROTO_UDP FREERTOS_IPPROTO_UDP
+#define AF_INET FREERTOS_AF_INET
+#define SOCK_STREAM FREERTOS_SOCK_STREAM
+#define SOCK_DGRAM FREERTOS_SOCK_DGRAM
+#define SO_BROADCAST 0
+#define SO_ERROR 0
+#define SOL_SOCKET 0
+#define SO_REUSEADDR 0
+#define sockaddr_in freertos_sockaddr
+#define sockaddr freertos_sockaddr
+#define accept(a, b, c) FreeRTOS_accept((a), (b), (c))
+#define connect(a, b, c) FreeRTOS_connect((a), (b), (c))
+#define bind(a, b, c) FreeRTOS_bind((a), (b), (c))
+#define listen(a, b) FreeRTOS_listen((a), (b))
+#define socket(a, b, c) FreeRTOS_socket((a), (b), (c))
+#define send(a, b, c, d) FreeRTOS_send((a), (b), (c), (d))
+#define recv(a, b, c, d) FreeRTOS_recv((a), (b), (c), (d))
+#define setsockopt(a, b, c, d, e) FreeRTOS_setsockopt((a), (b), (c), (d), (e))
+#define sendto(a, b, c, d, e, f) FreeRTOS_sendto((a), (b), (c), (d), (e), (f))
+#define recvfrom(a, b, c, d, e, f) \
+  FreeRTOS_recvfrom((a), (b), (c), (d), (e), (f))
+#define closesocket(x) FreeRTOS_closesocket(x)
+#define gethostbyname(x) FreeRTOS_gethostbyname(x)
+#define getsockname(a, b, c) mg_getsockname((a), (b), (c))
+#define getpeername(a, b, c) mg_getpeername((a), (b), (c))
+
+static inline int mg_getsockname(MG_SOCKET_TYPE fd, void *buf, socklen_t *len) {
+  (void) fd, (void) buf, (void) len;
+  return -1;
+}
+
+static inline int mg_getpeername(MG_SOCKET_TYPE fd, void *buf, socklen_t *len) {
+  (void) fd, (void) buf, (void) len;
+  return 0;
+}
+#endif
+
+
+#if defined(MG_ENABLE_LWIP) && MG_ENABLE_LWIP
+#if defined(__GNUC__)
+#include <sys/stat.h>
+#include <sys/time.h>
+#else
+struct timeval {
+  time_t tv_sec;
+  long tv_usec;
+};
+#endif
+
+#include <lwip/sockets.h>
+
+#if LWIP_SOCKET != 1
+// Sockets support disabled in LWIP by default
+#error Set LWIP_SOCKET variable to 1 (in lwipopts.h)
+#endif
+#endif
+
+
+#if defined(MG_ENABLE_RL) && MG_ENABLE_RL
+#include <rl_net.h>
+
+#define MG_ENABLE_CUSTOM_MILLIS 1
+#define closesocket(x) closesocket(x)
+#define mkdir(a, b) (-1)
+#define EWOULDBLOCK BSD_EWOULDBLOCK
+#define EAGAIN BSD_EWOULDBLOCK
+#define EINPROGRESS BSD_EWOULDBLOCK
+#define EINTR BSD_EWOULDBLOCK
+#define ECONNRESET BSD_ECONNRESET
+#define EPIPE BSD_ECONNRESET
+#define TCP_NODELAY SO_KEEPALIVE
+#endif
+
+
 #ifndef MG_ENABLE_LOG
 #define MG_ENABLE_LOG 1
 #endif
 
 #ifndef MG_ENABLE_MIP
-#define MG_ENABLE_MIP 0
+#define MG_ENABLE_MIP 0  // Mongoose built-in network stack
+#endif
+
+#ifndef MG_ENABLE_LWIP
+#define MG_ENABLE_LWIP 0  // lWIP network stack
+#endif
+
+#ifndef MG_ENABLE_FREERTOS_TCP
+#define MG_ENABLE_FREERTOS_TCP 0  // Amazon FreeRTOS-TCP network stack
+#endif
+
+#ifndef MG_ENABLE_RL
+#define MG_ENABLE_RL 0  // ARM MDK network stack
+#endif
+
+#ifndef MG_ENABLE_SOCKET
+#define MG_ENABLE_SOCKET !MG_ENABLE_MIP
 #endif
 
 #ifndef MG_ENABLE_POLL
@@ -646,10 +610,6 @@ int sscanf(const char *, const char *, ...);
 #define MG_ENABLE_FATFS 0
 #endif
 
-#ifndef MG_ENABLE_SOCKET
-#define MG_ENABLE_SOCKET 1
-#endif
-
 #ifndef MG_ENABLE_MBEDTLS
 #define MG_ENABLE_MBEDTLS 0
 #endif
@@ -1044,6 +1004,7 @@ enum {
 
 
 
+
 struct mg_dns {
   const char *url;          // DNS server URL
   struct mg_connection *c;  // DNS server connection
@@ -1071,7 +1032,7 @@ struct mg_mgr {
   int epoll_fd;                 // Used when MG_EPOLL_ENABLE=1
   void *priv;                   // Used by the MIP stack
   size_t extraconnsize;         // Used by the MIP stack
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif
 };
diff --git a/src/arch.h b/src/arch.h
index 18a154ed..c7223bb7 100644
--- a/src/arch.h
+++ b/src/arch.h
@@ -1,19 +1,17 @@
 #pragma once
 
-#define MG_ARCH_CUSTOM 0
-#define MG_ARCH_UNIX 1
-#define MG_ARCH_WIN32 2
-#define MG_ARCH_ESP32 3
-#define MG_ARCH_ESP8266 4
-#define MG_ARCH_FREERTOS_TCP 5
-#define MG_ARCH_FREERTOS_LWIP 6
-#define MG_ARCH_AZURERTOS 7
-#define MG_ARCH_RTX_LWIP 8
-#define MG_ARCH_ZEPHYR 9
-#define MG_ARCH_NEWLIB 10
-#define MG_ARCH_RTX 11
-#define MG_ARCH_TIRTOS 12
-#define MG_ARCH_RP2040 13
+#define MG_ARCH_CUSTOM 0     // User creates its own mongoose_custom.h
+#define MG_ARCH_UNIX 1       // Linux, BSD, Mac, ...
+#define MG_ARCH_WIN32 2      // Windows
+#define MG_ARCH_ESP32 3      // ESP32
+#define MG_ARCH_ESP8266 4    // ESP8266
+#define MG_ARCH_FREERTOS 5   // FreeRTOS
+#define MG_ARCH_AZURERTOS 6  // MS Azure RTOS
+#define MG_ARCH_ZEPHYR 7     // Zephyr RTOS
+#define MG_ARCH_NEWLIB 8     // Bare metal ARM
+#define MG_ARCH_RTX 9        // Keil MDK RTX
+#define MG_ARCH_TIRTOS 10    // Texas Semi TI-RTOS
+#define MG_ARCH_RP2040 11    // Raspberry Pi RP2040
 
 #if !defined(MG_ARCH)
 #if defined(__unix__) || defined(__APPLE__)
@@ -27,7 +25,8 @@
 #elif defined(ESP_PLATFORM)
 #define MG_ARCH MG_ARCH_ESP32
 #elif defined(FREERTOS_IP_H)
-#define MG_ARCH MG_ARCH_FREERTOS_TCP
+#define MG_ARCH MG_ARCH_FREERTOS
+#define MG_ENABLE_FREERTOS_TCP 1
 #elif defined(AZURE_RTOS_THREADX)
 #define MG_ARCH MG_ARCH_AZURERTOS
 #elif defined(PICO_TARGET_NAME)
@@ -44,15 +43,17 @@
 #endif
 
 // http://esr.ibiblio.org/?p=5095
-#define MG_BIG_ENDIAN (*(uint16_t *)"\0\xff" < 0x100)
+#define MG_BIG_ENDIAN (*(uint16_t *) "\0\xff" < 0x100)
 
 #include "arch_esp32.h"
 #include "arch_esp8266.h"
-#include "arch_freertos_lwip.h"
-#include "arch_freertos_tcp.h"
+#include "arch_freertos.h"
 #include "arch_newlib.h"
 #include "arch_rtx.h"
-#include "arch_rtx_lwip.h"
 #include "arch_unix.h"
 #include "arch_win32.h"
 #include "arch_zephyr.h"
+
+#include "net_ft.h"
+#include "net_lwip.h"
+#include "net_rl.h"
diff --git a/src/arch_freertos_lwip.h b/src/arch_freertos.h
similarity index 52%
rename from src/arch_freertos_lwip.h
rename to src/arch_freertos.h
index 840855d9..4be2b4de 100644
--- a/src/arch_freertos_lwip.h
+++ b/src/arch_freertos.h
@@ -1,8 +1,9 @@
 #pragma once
 
-#if MG_ARCH == MG_ARCH_FREERTOS_LWIP
+#if MG_ARCH == MG_ARCH_FREERTOS
 
 #include <ctype.h>
+// #include <errno.h> // Cannot include errno - might conflict with lwip!
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -10,40 +11,29 @@
 #include <stdio.h>
 #include <string.h>
 
-#if defined(__GNUC__)
-#include <sys/stat.h>
-#include <sys/time.h>
-#else
-struct timeval {
-  time_t tv_sec;
-  long tv_usec;
-};
-#endif
-
 #include <FreeRTOS.h>
 #include <task.h>
 
-#include <lwip/sockets.h>
-
-#if LWIP_SOCKET != 1
-// Sockets support disabled in LWIP by default
-#error Set LWIP_SOCKET variable to 1 (in lwipopts.h)
-#endif
-
-// Re-route calloc/free to the FreeRTOS's functions, don't use stdlib
-static inline void *mg_calloc(int cnt, size_t size) {
-  void *p = pvPortMalloc(cnt * size);
-  if (p != NULL) memset(p, 0, size * cnt);
-  return p;
-}
-#define calloc(a, b) mg_calloc((a), (b))
-#define free(a) vPortFree(a)
-#define malloc(a) pvPortMalloc(a)
-#define strdup(s) ((char *) mg_strdup(mg_str(s)).ptr)
-#define mkdir(a, b) (-1)
-
 #ifndef MG_IO_SIZE
 #define MG_IO_SIZE 512
 #endif
 
-#endif  // MG_ARCH == MG_ARCH_FREERTOS_LWIP
+#define calloc(a, b) mg_calloc(a, b)
+#define free(a) vPortFree(a)
+#define malloc(a) pvPortMalloc(a)
+#define strdup(s) ((char *) mg_strdup(mg_str(s)).ptr)
+
+// Re-route calloc/free to the FreeRTOS's functions, don't use stdlib
+static inline void *mg_calloc(size_t cnt, size_t size) {
+  void *p = pvPortMalloc(cnt * size);
+  if (p != NULL) memset(p, 0, size * cnt);
+  return p;
+}
+
+#define mkdir(a, b) mg_mkdir(a, b)
+static inline int mg_mkdir(const char *path, mode_t mode) {
+  (void) path, (void) mode;
+  return -1;
+}
+
+#endif  // MG_ARCH == MG_ARCH_FREERTOS
diff --git a/src/arch_rtx.h b/src/arch_rtx.h
index 8b7dfbc5..f364c16b 100644
--- a/src/arch_rtx.h
+++ b/src/arch_rtx.h
@@ -13,18 +13,8 @@
 #include <string.h>
 #include <time.h>
 
-#include <rl_net.h>
-
-#define MG_ENABLE_CUSTOM_MILLIS 1
-typedef int socklen_t;
-#define closesocket(x) closesocket(x)
-#define mkdir(a, b) (-1)
-#define EWOULDBLOCK BSD_EWOULDBLOCK
-#define EAGAIN BSD_EWOULDBLOCK
-#define EINPROGRESS BSD_EWOULDBLOCK
-#define EINTR BSD_EWOULDBLOCK
-#define ECONNRESET BSD_ECONNRESET
-#define EPIPE BSD_ECONNRESET
-#define TCP_NODELAY SO_KEEPALIVE
+#if !defined MG_ENABLE_RL && (!defined(MG_ENABLE_LWIP) || !MG_ENABLE_LWIP)
+#define MG_ENABLE_RL 1
+#endif
 
 #endif
diff --git a/src/config.h b/src/config.h
index ae3f71bf..bbcf94b5 100644
--- a/src/config.h
+++ b/src/config.h
@@ -5,7 +5,23 @@
 #endif
 
 #ifndef MG_ENABLE_MIP
-#define MG_ENABLE_MIP 0
+#define MG_ENABLE_MIP 0  // Mongoose built-in network stack
+#endif
+
+#ifndef MG_ENABLE_LWIP
+#define MG_ENABLE_LWIP 0  // lWIP network stack
+#endif
+
+#ifndef MG_ENABLE_FREERTOS_TCP
+#define MG_ENABLE_FREERTOS_TCP 0  // Amazon FreeRTOS-TCP network stack
+#endif
+
+#ifndef MG_ENABLE_RL
+#define MG_ENABLE_RL 0  // ARM MDK network stack
+#endif
+
+#ifndef MG_ENABLE_SOCKET
+#define MG_ENABLE_SOCKET !MG_ENABLE_MIP
 #endif
 
 #ifndef MG_ENABLE_POLL
@@ -20,10 +36,6 @@
 #define MG_ENABLE_FATFS 0
 #endif
 
-#ifndef MG_ENABLE_SOCKET
-#define MG_ENABLE_SOCKET 1
-#endif
-
 #ifndef MG_ENABLE_MBEDTLS
 #define MG_ENABLE_MBEDTLS 0
 #endif
diff --git a/src/net.c b/src/net.c
index 24fd891f..21c345be 100644
--- a/src/net.c
+++ b/src/net.c
@@ -237,7 +237,7 @@ void mg_mgr_free(struct mg_mgr *mgr) {
   mgr->timers = NULL;  // Important. Next call to poll won't touch timers
   for (c = mgr->conns; c != NULL; c = c->next) c->is_closing = 1;
   mg_mgr_poll(mgr, 0);
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
   FreeRTOS_DeleteSocketSet(mgr->ss);
 #endif
   MG_DEBUG(("All connections closed"));
@@ -258,7 +258,7 @@ void mg_mgr_init(struct mg_mgr *mgr) {
   // clang-format off
   { WSADATA data; WSAStartup(MAKEWORD(2, 2), &data); }
   // clang-format on
-#elif MG_ARCH == MG_ARCH_FREERTOS_TCP
+#elif MG_ENABLE_FREERTOS_TCP
   mgr->ss = FreeRTOS_CreateSocketSet();
 #elif defined(__unix) || defined(__unix__) || defined(__APPLE__)
   // Ignore SIGPIPE signal, so if client cancels the request, it
diff --git a/src/net.h b/src/net.h
index b01b0fbf..5f539d0f 100644
--- a/src/net.h
+++ b/src/net.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "arch.h"
+#include "config.h"
 #include "event.h"
 #include "iobuf.h"
 #include "str.h"
@@ -33,7 +34,7 @@ struct mg_mgr {
   int epoll_fd;                 // Used when MG_EPOLL_ENABLE=1
   void *priv;                   // Used by the MIP stack
   size_t extraconnsize;         // Used by the MIP stack
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
   SocketSet_t ss;  // NOTE(lsm): referenced from socket struct
 #endif
 };
diff --git a/src/arch_freertos_tcp.h b/src/net_ft.h
similarity index 58%
rename from src/arch_freertos_tcp.h
rename to src/net_ft.h
index 62346d5b..0c43ea07 100644
--- a/src/arch_freertos_tcp.h
+++ b/src/net_ft.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if defined(MG_ENABLE_FREERTOS_TCP) && MG_ENABLE_FREERTOS_TCP
 
 #include <ctype.h>
 #include <errno.h>
@@ -50,45 +50,16 @@
   FreeRTOS_recvfrom((a), (b), (c), (d), (e), (f))
 #define closesocket(x) FreeRTOS_closesocket(x)
 #define gethostbyname(x) FreeRTOS_gethostbyname(x)
-#define getsockname(a, b, c) (-1)
-#define getpeername(a, b, c) 0
+#define getsockname(a, b, c) mg_getsockname((a), (b), (c))
+#define getpeername(a, b, c) mg_getpeername((a), (b), (c))
 
-// Re-route calloc/free to the FreeRTOS's functions, don't use stdlib
-static inline void *mg_calloc(int cnt, size_t size) {
-  void *p = pvPortMalloc(cnt * size);
-  if (p != NULL) memset(p, 0, size * cnt);
-  return p;
+static inline int mg_getsockname(MG_SOCKET_TYPE fd, void *buf, socklen_t *len) {
+  (void) fd, (void) buf, (void) len;
+  return -1;
 }
-#define calloc(a, b) mg_calloc((a), (b))
-#define free(a) vPortFree(a)
-#define malloc(a) pvPortMalloc(a)
-#define mkdir(a, b) (-1)
 
-#if !defined(__GNUC__)
-// copied from GCC on ARM; for some reason useconds are signed
-struct timeval {
-  time_t tv_sec;
-  long tv_usec;
-};
+static inline int mg_getpeername(MG_SOCKET_TYPE fd, void *buf, socklen_t *len) {
+  (void) fd, (void) buf, (void) len;
+  return 0;
+}
 #endif
-
-#ifndef EINPROGRESS
-#define EINPROGRESS pdFREERTOS_ERRNO_EINPROGRESS
-#endif
-#ifndef EWOULDBLOCK
-#define EWOULDBLOCK pdFREERTOS_ERRNO_EWOULDBLOCK
-#endif
-#ifndef EAGAIN
-#define EAGAIN pdFREERTOS_ERRNO_EAGAIN
-#endif
-#ifndef EINTR
-#define EINTR pdFREERTOS_ERRNO_EINTR
-#endif
-
-// FreeRTOS-TCP uses non-standard semantics for listen() backlog size. It is
-// not a backlog size for pending SYN connections, but a max socket number
-#ifndef MG_SOCK_LISTEN_BACKLOG_SIZE
-#define MG_SOCK_LISTEN_BACKLOG_SIZE 128
-#endif
-
-#endif  // MG_ARCH == MG_ARCH_FREERTOS_TCP
diff --git a/src/arch_rtx_lwip.h b/src/net_lwip.h
similarity index 52%
rename from src/arch_rtx_lwip.h
rename to src/net_lwip.h
index 9200a3ec..d137e919 100644
--- a/src/arch_rtx_lwip.h
+++ b/src/net_lwip.h
@@ -1,14 +1,6 @@
 #pragma once
 
-#if MG_ARCH == MG_ARCH_RTX_LWIP
-
-#include <ctype.h>
-#include <stdarg.h>
-#include <stdbool.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <string.h>
-
+#if defined(MG_ENABLE_LWIP) && MG_ENABLE_LWIP
 #if defined(__GNUC__)
 #include <sys/stat.h>
 #include <sys/time.h>
@@ -25,16 +17,4 @@ struct timeval {
 // Sockets support disabled in LWIP by default
 #error Set LWIP_SOCKET variable to 1 (in lwipopts.h)
 #endif
-
-#define mkdir(a, b) (-1)
-
-#ifndef MG_IO_SIZE
-#define MG_IO_SIZE 512
-#endif
-
-#ifndef MG_PATH_MAX
-#define MG_PATH_MAX 128
-#endif
-
-
 #endif
diff --git a/src/net_rl.h b/src/net_rl.h
new file mode 100644
index 00000000..28b7bd54
--- /dev/null
+++ b/src/net_rl.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#if defined(MG_ENABLE_RL) && MG_ENABLE_RL
+#include <rl_net.h>
+
+#define MG_ENABLE_CUSTOM_MILLIS 1
+#define closesocket(x) closesocket(x)
+#define mkdir(a, b) (-1)
+#define EWOULDBLOCK BSD_EWOULDBLOCK
+#define EAGAIN BSD_EWOULDBLOCK
+#define EINPROGRESS BSD_EWOULDBLOCK
+#define EINTR BSD_EWOULDBLOCK
+#define ECONNRESET BSD_ECONNRESET
+#define EPIPE BSD_ECONNRESET
+#define TCP_NODELAY SO_KEEPALIVE
+#endif
diff --git a/src/sock.c b/src/sock.c
index bf1a672e..6262d3a7 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -136,7 +136,7 @@ long mg_io_send(struct mg_connection *c, const void *buf, size_t len) {
   } else {
     n = send(FD(c), (char *) buf, len, MSG_NONBLOCKING);
 #if MG_ARCH == MG_ARCH_RTX
-    if (n == BSD_EWOULDBLOCK) return MG_IO_WAIT;
+    if (n == EWOULDBLOCK) return MG_IO_WAIT;
 #endif
   }
   if (n < 0 && mg_sock_would_block()) return MG_IO_WAIT;
@@ -166,11 +166,11 @@ static void mg_set_non_blocking_mode(MG_SOCKET_TYPE fd) {
 #elif MG_ARCH == MG_ARCH_RTX
   unsigned long on = 1;
   ioctlsocket(fd, FIONBIO, &on);
-#elif MG_ARCH == MG_ARCH_FREERTOS_TCP
+#elif MG_ENABLE_FREERTOS_TCP
   const BaseType_t off = 0;
   if (setsockopt(fd, 0, FREERTOS_SO_RCVTIMEO, &off, sizeof(off)) != 0) (void) 0;
   if (setsockopt(fd, 0, FREERTOS_SO_SNDTIMEO, &off, sizeof(off)) != 0) (void) 0;
-#elif MG_ARCH == MG_ARCH_FREERTOS_LWIP || MG_ARCH == MG_ARCH_RTX_LWIP
+#elif MG_ENABLE_LWIP
   lwip_fcntl(fd, F_SETFL, O_NONBLOCK);
 #elif MG_ARCH == MG_ARCH_AZURERTOS
   fcntl(fd, F_SETFL, O_NONBLOCK);
@@ -298,7 +298,7 @@ static void close_conn(struct mg_connection *c) {
     epoll_ctl(c->mgr->epoll_fd, EPOLL_CTL_DEL, FD(c), NULL);
 #endif
     closesocket(FD(c));
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
     FreeRTOS_FD_CLR(c->fd, c->mgr->ss, eSELECT_ALL);
 #endif
   }
@@ -320,7 +320,7 @@ static void connect_conn(struct mg_connection *c) {
 }
 
 static void setsockopts(struct mg_connection *c) {
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP || MG_ARCH == MG_ARCH_AZURERTOS || \
+#if MG_ENABLE_FREERTOS_TCP || MG_ARCH == MG_ARCH_AZURERTOS || \
     MG_ARCH == MG_ARCH_TIRTOS
   (void) c;
 #else
@@ -348,7 +348,8 @@ void mg_connect_resolved(struct mg_connection *c) {
 #if MG_ARCH == MG_ARCH_TIRTOS
     union usa usa;  // TI-RTOS NDK requires binding to receive on UDP sockets
     socklen_t slen = tousa(&c->loc, &usa);
-    if (bind(c->fd, &usa.sa, slen) != 0) MG_ERROR(("bind: %d", MG_SOCKET_ERRNO));
+    if (bind(c->fd, &usa.sa, slen) != 0)
+      MG_ERROR(("bind: %d", MG_SOCKET_ERRNO));
 #endif
     mg_call(c, MG_EV_RESOLVE, NULL);
     mg_call(c, MG_EV_CONNECT, NULL);
@@ -372,7 +373,8 @@ void mg_connect_resolved(struct mg_connection *c) {
   (void) rc;
 }
 
-static MG_SOCKET_TYPE raccept(MG_SOCKET_TYPE sock, union usa *usa, socklen_t len) {
+static MG_SOCKET_TYPE raccept(MG_SOCKET_TYPE sock, union usa *usa,
+                              socklen_t len) {
   MG_SOCKET_TYPE s = MG_INVALID_SOCKET;
   do {
     memset(usa, 0, sizeof(*usa));
@@ -394,8 +396,8 @@ static void accept_conn(struct mg_mgr *mgr, struct mg_connection *lsn) {
     if (MG_SOCKET_ERRNO != EAGAIN)
 #endif
       MG_ERROR(("%lu accept failed, errno %d", lsn->id, MG_SOCKET_ERRNO));
-#if (MG_ARCH != MG_ARCH_WIN32) && (MG_ARCH != MG_ARCH_FREERTOS_TCP) && \
-    (MG_ARCH != MG_ARCH_TIRTOS) && !(MG_ENABLE_POLL)
+#if (MG_ARCH != MG_ARCH_WIN32) && !MG_ENABLE_FREERTOS_TCP && \
+    (MG_ARCH != MG_ARCH_TIRTOS) && !MG_ENABLE_POLL
   } else if ((long) fd >= FD_SETSIZE) {
     MG_ERROR(("%ld > %ld", (long) fd, (long) FD_SETSIZE));
     closesocket(fd);
@@ -499,7 +501,7 @@ static bool skip_iotest(const struct mg_connection *c) {
 }
 
 static void mg_iotest(struct mg_mgr *mgr, int ms) {
-#if MG_ARCH == MG_ARCH_FREERTOS_TCP
+#if MG_ENABLE_FREERTOS_TCP
   struct mg_connection *c;
   for (c = mgr->conns; c != NULL; c = c->next) {
     c->is_readable = c->is_writable = 0;
@@ -511,8 +513,8 @@ static void mg_iotest(struct mg_mgr *mgr, int ms) {
   FreeRTOS_select(mgr->ss, pdMS_TO_TICKS(ms));
   for (c = mgr->conns; c != NULL; c = c->next) {
     EventBits_t bits = FreeRTOS_FD_ISSET(c->fd, mgr->ss);
-    c->is_readable = bits & (eSELECT_READ | eSELECT_EXCEPT) ? 1 : 0;
-    c->is_writable = bits & eSELECT_WRITE ? 1 : 0;
+    c->is_readable = bits & (eSELECT_READ | eSELECT_EXCEPT) ? 1U : 0;
+    c->is_writable = bits & eSELECT_WRITE ? 1U : 0;
     FreeRTOS_FD_CLR(c->fd, mgr->ss,
                     eSELECT_READ | eSELECT_EXCEPT | eSELECT_WRITE);
   }
diff --git a/src/util.c b/src/util.c
index 12924867..6f7f5c0c 100644
--- a/src/util.c
+++ b/src/util.c
@@ -96,9 +96,7 @@ uint64_t mg_millis(void) {
   return time_us_64() / 1000;
 #elif MG_ARCH == MG_ARCH_ESP32
   return esp_timer_get_time() / 1000;
-#elif MG_ARCH == MG_ARCH_ESP8266
-  return xTaskGetTickCount() * portTICK_PERIOD_MS;
-#elif MG_ARCH == MG_ARCH_FREERTOS_TCP || MG_ARCH == MG_ARCH_FREERTOS_LWIP
+#elif MG_ARCH == MG_ARCH_ESP8266 || MG_ARCH == MG_ARCH_FREERTOS
   return xTaskGetTickCount() * portTICK_PERIOD_MS;
 #elif MG_ARCH == MG_ARCH_AZURERTOS
   return tx_time_get() * (1000 /* MS per SEC */ / TX_TIMER_TICKS_PER_SECOND);
diff --git a/test/unit_test.c b/test/unit_test.c
index 488059ca..e6a3ec7a 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -331,10 +331,10 @@ static void test_sntp(void) {
 
   ASSERT(mg_sntp_parse(bad, sizeof(bad)) < 0);
   ASSERT(mg_sntp_parse(NULL, 0) == -1);
-  // test_sntp_server("udp://time.windows.com:123");
   // NOTE(cpq): temporarily disabled until Github Actions fix their NTP
   // port blockage issue, https://github.com/actions/runner-images/issues/5615
-  test_sntp_server("udp://time.apple.com:123");
+  //test_sntp_server("udp://time.apple.com:123");
+  test_sntp_server("udp://time.windows.com:123");
   test_sntp_server(NULL);
 }