mongoose/docs/overview/usage-example.md

---
title: Example - TCP echo server
---

- Copy `mongoose.c` and `mongoose.h` to your build tree
- Write code that uses the Mongoose API, e.g. in `my_app.c`
- Compile application: `$ cc my_app.c mongoose.c`

```c
#include "mongoose.h"  // Include Mongoose API definitions

// Define an event handler function
static void ev_handler(struct mg_connection *nc, int ev, void *ev_data) {
  struct mbuf *io = &nc->recv_mbuf;

  switch (ev) {
    case MG_EV_RECV:
      // This event handler implements simple TCP echo server
      mg_send(nc, io->buf, io->len);  // Echo received data back
      mbuf_remove(io, io->len);      // Discard data from recv buffer
      break;
    default:
      break;
  }
}

int main(void) {
  struct mg_mgr mgr;

  mg_mgr_init(&mgr, NULL);  // Initialize event manager object

  // Note that many connections can be added to a single event manager
  // Connections can be created at any point, e.g. in event handler function
  mg_bind(&mgr, "1234", ev_handler);  // Create listening connection and add it to the event manager

  for (;;) {  // Start infinite event loop
    mg_mgr_poll(&mgr, 1000);
  }

  mg_mgr_free(&mgr);
  return 0;
}
```