AT ESP8266 UDP通信

esp8266 udp server 端口监听错误

发布于 2023-03-22 11:24:12 浏览：102 订阅该版

1、使用esp8266 at组件+sal socket实现使用udpserver_sample.c demo代码 udp server，通信失败
2、跟踪代码发现 packegs 里面 
```c
static int esp8266_socket_connect(struct at_socket *socket, char *ip, int32_t port, enum at_socket_type type, rt_bool_t is_client)
```
这个接口封装的at指令，需要server的port，并且 AT+CIPSTART入参需要 udp remote_port和local_port ,但实际传入的port并非初始化sokcet的bind的local_port，而是只有remote_port
3、代码分析
```c
int at_recvfrom(int socket, void *mem, size_t len, int flags, struct sockaddr *from, socklen_t *fromlen)
{
	...
	 if (from && sock->type == AT_SOCKET_UDP && sock->state == AT_SOCKET_OPEN)
    {
        ip_addr_t remote_addr;
        uint16_t remote_port = 0;
        char ipstr[16] = { 0 };

socketaddr_to_ipaddr_port(from, &remote_addr, &remote_port);
        ipaddr_to_ipstr(from, ipstr);

if (sock->ops->at_connect(sock, ipstr, remote_port, sock->type, RT_FALSE) < 0)
        {
            result = -1;
            goto __exit;
        }
        sock->state = AT_SOCKET_CONNECT;
    }
	...
}
```
sock->ops->at_connect 传入port是remote_port，并非bind local port
4、修改esp8266 packges at 命令封装 
```c
if (at_obj_exec_cmd(device->client, resp,
                                "AT+CIPSTART=%d,\"UDP\",\"%s\",%d,%d", device_socket, ip,port, port) < 0)
```
修改at_socket中 at_connect 入参，把remote_port 换成sock->listen.port
```c
if (sock->ops->at_connect(sock, ipstr, sock->listen.port, sock->type, RT_FALSE) < 0)
```