Added plain TCP server and client example

examples/tcp/Makefile

@@ -0,0 +1,20 @@
+PROG ?= example
+SSL = ?
+
+ifeq "$(SSL)" "MBEDTLS"
+CFLAGS += -DMG_ENABLE_MBEDTLS=1 -lmbedtls -lmbedcrypto -lmbedx509
+endif
+
+ifeq "$(SSL)" "OPENSSL"
+CFLAGS += -DMG_ENABLE_OPENSSL=1 -lssl -lcrypto
+endif
+
+all: $(PROG)
+	$(DEBUGGER) ./$(PROG) $(ARGS)
+
+
+$(PROG): main.c
+	$(CC) ../../mongoose.c -I../.. -W -Wall $(CFLAGS) $(EXTRA_CFLAGS) -o $(PROG) main.c
+
+clean:
+	rm -rf $(PROG) *.o *.dSYM *.gcov *.gcno *.gcda *.obj *.exe *.ilk *.pdb

examples/tcp/main.c

@@ -0,0 +1,96 @@
+// Copyright (c) 2022 Cesanta Software Limited
+// All rights reserved
+
+#include "mongoose.h"
+
+static const char *s_lsn = "tcp://localhost:8765";   // Listening address
+static const char *s_conn = "tcp://localhost:8765";  // Connect to address
+
+// client resources
+static struct c_res_s {
+  int i;
+  struct mg_connection *c;
+} c_res;
+
+// CLIENT event handler
+static void cfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+  int *i = &((struct c_res_s *) fn_data)->i;
+  if (ev == MG_EV_OPEN) {
+    MG_INFO(("CLIENT has been initialized"));
+  } else if (ev == MG_EV_CONNECT) {
+    MG_INFO(("CLIENT connected"));
+    *i = 1;  // do something
+  } else if (ev == MG_EV_READ) {
+    struct mg_iobuf *r = &c->recv;
+    MG_INFO(("CLIENT got data: %.*s", r->len, r->buf));
+  } else if (ev == MG_EV_CLOSE) {
+    MG_INFO(("CLIENT disconnected"));
+    // signal we are done
+    ((struct c_res_s *) fn_data)->c = NULL;
+  } else if (ev == MG_EV_ERROR) {
+    MG_INFO(("CLIENT error: %s", (char *) ev_data));
+  } else if (ev == MG_EV_POLL && *i != 0) {
+    switch ((*i)++) {
+      case 50:  // 50 x 100ms = 5s
+        mg_send(c, "Hi, there", 9);
+        MG_INFO(("CLIENT sent data"));
+        break;
+      case 100:  // another 5s
+        // send any possible outstanding data and close the connection
+        c->is_draining = 1;
+        break;
+    }
+  }
+}
+
+// SERVER event handler
+static void sfn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
+  if (ev == MG_EV_OPEN && c->is_listening == 1) {
+    MG_INFO(("SERVER is listening"));
+  } else if (ev == MG_EV_ACCEPT) {
+    MG_INFO(("SERVER accepted a connection"));
+  } else if (ev == MG_EV_READ) {
+    struct mg_iobuf *r = &c->recv;
+    MG_INFO(("SERVER got data: %.*s", r->len, r->buf));
+    mg_send(c, r->buf, r->len);  // echo it back
+  } else if (ev == MG_EV_CLOSE) {
+    MG_INFO(("SERVER disconnected"));
+  } else if (ev == MG_EV_ERROR) {
+    MG_INFO(("SERVER error: %s", (char *) ev_data));
+  }
+  (void) fn_data;
+}
+
+// Timer function - recreate client connection if it is closed
+static void timer_fn(void *arg) {
+  struct mg_mgr *mgr = (struct mg_mgr *) arg;
+  if (c_res.c == NULL) {
+    // connect
+    c_res.i = 0;
+    c_res.c = mg_connect(mgr, s_conn, cfn, &c_res);
+    if (c_res.c == NULL)
+      MG_INFO(("CLIENT cant' open a connection"));
+    else
+      MG_INFO(("CLIENT is connecting"));
+  }
+}
+
+int main(void) {
+  struct mg_mgr mgr;  // Event manager
+  struct mg_connection *c;
+
+  mg_log_set("2");    // Set to 0 to disable debug
+  mg_mgr_init(&mgr);  // Initialize event manager
+  mg_timer_add(&mgr, 15000, MG_TIMER_REPEAT | MG_TIMER_RUN_NOW, timer_fn,
+               &mgr);                     // Init timer for demo purposes, 15s
+  c = mg_listen(&mgr, s_lsn, sfn, NULL);  // Create server connection
+  if (c == NULL) {
+    MG_INFO(("SERVER cant' open a connection"));
+    return 0;
+  }
+  while (true)
+    mg_mgr_poll(&mgr, 100);  // Infinite event loop, blocks for upto 100ms
+                             // unless there is network activity
+  mg_mgr_free(&mgr);         // Free resources
+  return 0;
+}