Merge pull request #3423 from cesanta/singleton

Add http singleton client example

tutorials/http/singleton-client/Makefile

@@ -0,0 +1,28 @@
+PROG ?= example                   # Program we are building
+DELETE = rm -rf                   # Command to remove files
+OUT ?= -o $(PROG)                 # Compiler argument for output file
+SOURCES = main.c mongoose.c       # Source code files
+CFLAGS = -W -Wall -Wextra -g -I.  # Build options
+#CFLAGS += -fsanitize=address,undefined,alignment
+
+# Mongoose build options. See https://mongoose.ws/documentation/#build-options
+CFLAGS_MONGOOSE += -DMG_ENABLE_LINES=1
+CFLAGS_MONGOOSE += -DMG_TLS=MG_TLS_BUILTIN
+#CFLAGS_MONGOOSE += -DMG_TLS=MG_TLS_OPENSSL -L/opt/homebrew/opt/openssl/lib -I/opt/homebrew/opt/openssl/include -lssl -lcrypto
+#CFLAGS_MONGOOSE += -DMG_TLS=MG_TLS_MBED -L/opt/homebrew/opt/mbedtls/lib -I/opt/homebrew/opt/mbedtls/include -lmbedtls -lmbedcrypto -lmbedx509
+
+ifeq ($(OS),Windows_NT)   # Windows settings. Assume MinGW compiler. To use VC: make CC=cl CFLAGS=/MD OUT=/Feprog.exe
+  PROG ?= example.exe           # Use .exe suffix for the binary
+  CC = gcc                      # Use MinGW gcc compiler
+  CFLAGS += -lws2_32 -lbcrypt   # Link against Winsock library
+  DELETE = cmd /C del /Q /F /S  # Command prompt command to delete files
+endif
+
+all: $(PROG)              # Default target. Build and run program
+	$(RUN) ./$(PROG) $(ARGS)
+
+$(PROG): $(SOURCES)       # Build program from sources
+	$(CC) $(SOURCES) $(CFLAGS) $(CFLAGS_MONGOOSE) $(CFLAGS_EXTRA) $(OUT)
+
+clean:                    # Cleanup. Delete built program and all build artifacts
+	$(DELETE) $(PROG) *.o *.obj *.exe *.dSYM

tutorials/http/singleton-client/main.c

@@ -0,0 +1,111 @@
+// Copyright (c) 2026 Cesanta Software Limited
+// All rights reserved
+//
+// This example shows how we can poll an external HTTP server periodically, and
+// make sure that not more than one instance of the active request in flight.
+// Each request has a configured timeout.
+
+#include "mongoose.h"
+
+static const char *s_url = "https://mongoose.ws/tls/api/ca";
+static const char *s_post_data = "hi";
+static const uint64_t s_connect_timeout_ms = 5500;  // milliseconds
+static struct mg_connection *s_conn = NULL;
+
+// TLS certificate, obtained using https://mongoose.ws/tls/
+#define TLS_CA                                                         \
+  "-----BEGIN CERTIFICATE-----\n"                                      \
+  "MIIEVjCCAj6gAwIBAgIQY5WTY8JOcIJxWRi/w9ftVjANBgkqhkiG9w0BAQsFADBP\n" \
+  "MQswCQYDVQQGEwJVUzEpMCcGA1UEChMgSW50ZXJuZXQgU2VjdXJpdHkgUmVzZWFy\n" \
+  "Y2ggR3JvdXAxFTATBgNVBAMTDElTUkcgUm9vdCBYMTAeFw0yNDAzMTMwMDAwMDBa\n" \
+  "Fw0yNzAzMTIyMzU5NTlaMDIxCzAJBgNVBAYTAlVTMRYwFAYDVQQKEw1MZXQncyBF\n" \
+  "bmNyeXB0MQswCQYDVQQDEwJFODB2MBAGByqGSM49AgEGBSuBBAAiA2IABNFl8l7c\n" \
+  "S7QMApzSsvru6WyrOq44ofTUOTIzxULUzDMMNMchIJBwXOhiLxxxs0LXeb5GDcHb\n" \
+  "R6EToMffgSZjO9SNHfY9gjMy9vQr5/WWOrQTZxh7az6NSNnq3u2ubT6HTKOB+DCB\n" \
+  "9TAOBgNVHQ8BAf8EBAMCAYYwHQYDVR0lBBYwFAYIKwYBBQUHAwIGCCsGAQUFBwMB\n" \
+  "MBIGA1UdEwEB/wQIMAYBAf8CAQAwHQYDVR0OBBYEFI8NE6L2Ln7RUGwzGDhdWY4j\n" \
+  "cpHKMB8GA1UdIwQYMBaAFHm0WeZ7tuXkAXOACIjIGlj26ZtuMDIGCCsGAQUFBwEB\n" \
+  "BCYwJDAiBggrBgEFBQcwAoYWaHR0cDovL3gxLmkubGVuY3Iub3JnLzATBgNVHSAE\n" \
+  "DDAKMAgGBmeBDAECATAnBgNVHR8EIDAeMBygGqAYhhZodHRwOi8veDEuYy5sZW5j\n" \
+  "ci5vcmcvMA0GCSqGSIb3DQEBCwUAA4ICAQBnE0hGINKsCYWi0Xx1ygxD5qihEjZ0\n" \
+  "RI3tTZz1wuATH3ZwYPIp97kWEayanD1j0cDhIYzy4CkDo2jB8D5t0a6zZWzlr98d\n" \
+  "AQFNh8uKJkIHdLShy+nUyeZxc5bNeMp1Lu0gSzE4McqfmNMvIpeiwWSYO9w82Ob8\n" \
+  "otvXcO2JUYi3svHIWRm3+707DUbL51XMcY2iZdlCq4Wa9nbuk3WTU4gr6LY8MzVA\n" \
+  "aDQG2+4U3eJ6qUF10bBnR1uuVyDYs9RhrwucRVnfuDj29CMLTsplM5f5wSV5hUpm\n" \
+  "Uwp/vV7M4w4aGunt74koX71n4EdagCsL/Yk5+mAQU0+tue0JOfAV/R6t1k+Xk9s2\n" \
+  "HMQFeoxppfzAVC04FdG9M+AC2JWxmFSt6BCuh3CEey3fE52Qrj9YM75rtvIjsm/1\n" \
+  "Hl+u//Wqxnu1ZQ4jpa+VpuZiGOlWrqSP9eogdOhCGisnyewWJwRQOqK16wiGyZeR\n" \
+  "xs/Bekw65vwSIaVkBruPiTfMOo0Zh4gVa8/qJgMbJbyrwwG97z/PRgmLKCDl8z3d\n" \
+  "tA0Z7qq7fta0Gl24uyuB05dqI5J1LvAzKuWdIjT1tP8qCoxSE/xpix8hX2dt3h+/\n" \
+  "jujUgFPFZ0EVZ0xSyBNRF3MboGZnYXFUxpNjTWPKpagDHJQmqrAcDmWJnMsFY3jS\n" \
+  "u1igv3OefnWjSQ==\n"                                                 \
+  "-----END CERTIFICATE-----"
+
+static void http_ev_handler(struct mg_connection *c, int ev, void *ev_data) {
+  uint64_t *start_time = (uint64_t *) c->data;  // Stored start time
+  bool *success = (bool *) (start_time + 1);    // Stored success flag
+  if (ev == MG_EV_OPEN) {
+    *start_time = mg_millis();
+    MG_DEBUG(("%lu Connection started, time: %llu", c->id, *start_time));
+  } else if (ev == MG_EV_POLL) {
+    if (*start_time + s_connect_timeout_ms < mg_millis()) {
+      mg_error(c, "Connect timeout");
+    }
+  } else if (ev == MG_EV_CONNECT) {
+    // Connected to server. Extract host name from URL
+    struct mg_str host = mg_url_host(s_url);
+    if (c->is_tls) {
+      struct mg_tls_opts opts = {};
+      opts.ca = mg_str(TLS_CA);
+      opts.name = host;
+      mg_tls_init(c, &opts);
+    }
+    // Send request
+    int content_length = s_post_data ? strlen(s_post_data) : 0;
+    mg_printf(c,
+              "%s %s HTTP/1.0\r\n"
+              "Host: %.*s\r\n"
+              "Content-Type: octet-stream\r\n"
+              "Content-Length: %d\r\n"
+              "\r\n",
+              s_post_data ? "POST" : "GET", mg_url_uri(s_url), host.len,
+              host.buf, content_length);
+    mg_send(c, s_post_data, content_length);
+  } else if (ev == MG_EV_HTTP_MSG) {
+    // Response is received. Print it
+    struct mg_http_message *hm = (struct mg_http_message *) ev_data;
+    MG_INFO(("%lu Got response %lu bytes %lu", c->id, hm->body.len, c->rtls.len));
+    *success = true;
+    c->is_closing = 1;
+  } else if (ev == MG_EV_ERROR) {
+    MG_ERROR(("%lu Connection error: %s", c->id, ev_data));
+  } else if (ev == MG_EV_CLOSE) {
+    MG_DEBUG(("%lu Connection closed %lu", c->id, mg_millis() - *start_time));
+    if (*success == false) MG_ERROR(("%lu NO RESPONSE %lu", c->id, c->rtls.len));
+    if (c->is_draining == 0) s_conn = NULL;
+  }
+}
+
+static void timer_fn(void *arg) {
+  struct mg_mgr *mgr = (struct mg_mgr *) arg;
+  // If connection is already there, do nothing. Otherwise, start it
+  if (s_conn != NULL) {
+    MG_DEBUG(("Connection is already active..."));
+  } else {
+    s_conn = mg_http_connect(mgr, s_url, http_ev_handler, NULL);
+  }
+}
+
+int main(void) {
+  struct mg_mgr mgr;
+  mg_log_set(MG_LL_INFO);
+  mg_mgr_init(&mgr);
+
+  // Attempt to start a POST request frequently
+  mg_timer_add(&mgr, 50, MG_TIMER_REPEAT, timer_fn, &mgr);
+
+  for (;;) mg_mgr_poll(&mgr, 10);
+  mg_mgr_free(&mgr);
+
+  return 0;
+}

tutorials/http/singleton-client/mongoose.c

@@ -0,0 +1 @@
+../../../mongoose.c

tutorials/http/singleton-client/mongoose.h

@@ -0,0 +1 @@
+../../../mongoose.h