NetConn LWIP TCP/IP客户端[Freertos]

Question

我使用下面的代码为嵌入式项目创建一个TCP客户端：

NetConn和NetBuf Creation

static struct netconn *conn;
static struct netbuf *buf;
static ip_addr_t *addr, dest_addr;
static unsigned short port, dest_port;
char msgc[100];
char smsgc[200];
int indx = 0;

void tcpinit_thread()
{
err_t connect_error;

/* Create a new connection identifier. */
conn = netconn_new(NETCONN_TCP);

if (conn!=NULL)
{

    /* The desination IP adress of the computer */
    IP_ADDR4(&dest_addr, 192, 168, 225, 20);
    dest_port = 5656;  // server port

    /* Connect to the TCP Server */
    connect_error = netconn_connect(conn, &dest_addr, dest_port);

    // If the connection to the server is established, the following will continue, else delete the connection
    if (connect_error == ERR_OK)
    {
        printf("TCP client connected on port 5656 \r\n");
        while (1)
        {
            /* wait until the data is sent by the server */
            if (netconn_recv(conn, &buf) == ERR_OK)
            {
                /* Extract the address and port in case they are required */
                addr = netbuf_fromaddr(buf);  // get the address of the client
                port = netbuf_fromport(buf);  // get the Port of the client

                /* If there is some data remaining to be sent, the following process will continue */
                do
                {

                    strncpy (msgc, buf->p->payload, buf->p->len);   // get the message from the server

                    // Or modify the message received, so that we can send it back to the server
                    sprintf (smsgc, "\"%s\" was sent by the Server\n", msgc);
                    printf("data received from server \r\n");
                    // send the data to the TCP Server
                    tcpsend (smsgc);

                    memset (msgc, '\0', 100);  // clear the buffer
                }
                while (netbuf_next(buf) >0);

                netbuf_delete(buf);
            }
        }
    }

    else
    {
        /* Close connection and discard connection identifier. */
        netconn_close(conn);
        netconn_delete(conn);
        printf("Client disconnected \r\n");
    }
}

}

来发送数据

void tcpsend (char *data)
{
// send the data to the connected connection
netconn_write(conn, data, strlen(data), NETCONN_COPY);
}

INIT inith inith thread

void tcpclient_init (void)
{
sys_thread_new("tcpinit_thread", tcpinit_thread, NULL, 1024,DEFAULT_THREAD_PRIO);
}

问题，即使它在指定的端口上运行，我也无法连接到服务器。 我总是得到错误13：连接中止。

所以我只是想知道我做错了什么？