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TCP and UDP Socket Tutorial

Overview​

This tutorial explains how to use TAL network sockets for TCP and UDP. The TCP client walkthrough matches examples/protocols/tcp_client (PROTOCOL_TCP, tal_net_connect, tal_net_send). UDP is illustrated with PROTOCOL_UDP, tal_net_bind, tal_net_send_to, and tal_net_recvfrom; a concrete UDP broadcast sample lives in examples/wifi/ap.

Prerequisites​

Requirements​

  • Target that builds examples/protocols/tcp_client with tal_network and (typically) Wi-Fi.
  • A reachable TCP server. The default sample uses 127.0.0.1 and port 7; on hardware set TCP_SERVER_IP to your PC or server LAN address and open the port.
  • For UDP experiments, a peer IP/port or a broadcast-capable LAN (see the Wi-Fi AP example).

Steps (TCP client)​

  1. Open examples/protocols/tcp_client.

  2. Set TCP_SERVER_IP and TCP_SERVER_PORT in src/example_tcp_client.c.

  3. Configure Wi-Fi credentials in the same file when ENABLE_WIFI is defined.

  4. Build and run:

    cd examples/protocols/tcp_client
    tos.py config choice
    tos.py build

  5. After the network is up, the task creates a PROTOCOL_TCP socket, resolves the address with tal_net_str2addr, calls tal_net_connect, sends a small buffer several times with tal_net_send, then tal_net_close.

Expected outcome: The server receives repeated payloads; device logs show connect and send success.

TCP client code pattern​

#include "tal_network.h"

int sock_fd = tal_net_socket_create(PROTOCOL_TCP);
TUYA_IP_ADDR_T server_ip = tal_net_str2addr(TCP_SERVER_IP);

if (tal_net_connect(sock_fd, server_ip, TCP_SERVER_PORT) < 0) {
    PR_ERR("connect failed");
    tal_net_close(sock_fd);
    return;
}

const char msg[] = "Hello Tuya\n";
tal_net_send(sock_fd, msg, strlen(msg));
tal_net_close(sock_fd);

For a TCP server, use examples/protocols/tcp_server (tal_net_bind, tal_net_listen, tal_net_accept, tal_net_recv).

UDP send and receive​

Create a UDP socket with PROTOCOL_UDP. For a simple unicast client that sends to a known host and reads one reply:

#include "tal_network.h"

#define LOCAL_PORT  45000
#define REMOTE_PORT 45001

int udp_fd = tal_net_socket_create(PROTOCOL_UDP);
if (udp_fd < 0) {
    PR_ERR("udp create failed");
    return;
}

TUYA_IP_ADDR_T local_ip = tal_net_str2addr("192.168.1.50"); /* your interface address */
if (tal_net_bind(udp_fd, local_ip, LOCAL_PORT) < 0) {
    PR_ERR("bind failed");
    tal_net_close(udp_fd);
    return;
}

const char payload[] = "ping";
TUYA_IP_ADDR_T peer_ip = tal_net_str2addr("192.168.1.100");
tal_net_send_to(udp_fd, payload, strlen(payload), peer_ip, REMOTE_PORT);

char rx[256];
TUYA_IP_ADDR_T from_addr = 0;
uint16_t from_port = 0;
TUYA_ERRNO n = tal_net_recvfrom(udp_fd, rx, sizeof(rx), &from_addr, &from_port);
if (n > 0) {
    PR_DEBUG("got %d bytes from port %u", (int)n, (unsigned)from_port);
}
tal_net_close(udp_fd);

Replace local_ip with the IPv4 address of the interface you want to bind; the exact value depends on your netmgr or static config.

UDP broadcast reference​

Broadcast (periodic beacon on the AP subnet) is implemented in examples/wifi/ap/src/example_wifi_ap.c: tal_net_socket_create(PROTOCOL_UDP), tal_net_bind, tal_net_set_broadcast, and tal_net_send_to with address 0xFFFFFFFF and a chosen port.

Implementation notes​

  • Check return values of tal_net_connect, tal_net_send, tal_net_send_to, and tal_net_recvfrom; negative values indicate errors per the adapter.
  • Use tal_net_set_block or tal_net_select if you need timeouts or non-blocking I/O.
  • TCP is connection-oriented; UDP is datagram based—each tal_net_send_to is one packet unless the stack fragments.

References​

  • TCP client: examples/protocols/tcp_client/src/example_tcp_client.c
  • TCP server: examples/protocols/tcp_server
  • UDP broadcast: examples/wifi/ap/src/example_wifi_ap.c
  • API: src/tal_network/include/tal_network.h
  • Wi-Fi Station tutorial
  • Examples index