4.3 TCP客户端通信

本节我们使用开发板建立一个 tcp 客户端，再去连接指定地址和端口的 tcp 服务端并进行数据通信。打开宏定义 DEMO_SOCKET_CLIENT_SERVER、DEMO_CONNECT_NET；

在开发板连网成功后，创建TCP连接。
int demo_socket_client(char *ssid, char *pwd,int port,char *ip)
{
struct tls_ethif * ethif;
c_connect_wifi(ssid,pwd);
while(1)
{
tls_os_time_delay(1);
ethif = tls_netif_get_ethif();
if(ethif->status)
break;
}
socket_client_connect(port,ip);
return 0;
}
创建一个socket连接，连接指定目标的TCP服务器。
static int socket_client_connect(int port, char *ip)
{
int ret;
char sock_rx[DEMO_SOCK_BUF_SIZE] = {0};
struct sockaddr_in pin;
printf("port:%d,ip:%s\n",port,ip);
while(1)
{
memset(&pin, 0, sizeof(struct sockaddr));
pin.sin_family=AF_INET;

	pin.sin_addr.s_addr = ipaddr_addr(ip);
	pin.sin_port=htons(port);
	if((socket_num = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP)) < 0)
	{
		printf("creat socket fail, errno:%d\n",errno);
		return -1;
	}
	
	if (connect(socket_num, (struct sockaddr *)&pin, sizeof(struct sockaddr)) != 0)
	{
    	printf("connect fail errno:%d\n",errno);
	}
	else
	{
		printf("connect success\n");
	}
	while(1)
	{
		tls_os_time_delay(1000);
		ret = send(socket_num, sock_tx, strlen(sock_tx), 0);
		if(ret < 0)
		{
			printf("Error occured during sending, errno:%d\n",errno);
			break;
		}
		
        ret = recv(socket_num, sock_rx, sizeof(sock_rx)-1, 0);	
		if(ret < 0)
		{
			printf("Receive failed, errno:%d\n",errno);
			break;
		}
		else
		{
			sock_rx[ret] = 0;
            printf("\nReceive %d bytes from %s\n",ret,ip);	
			printf("%s\n",sock_rx);
		}
		tls_os_time_delay(2);
	}
	if(socket_num != -1)
	{
		printf("shutting down socket and restaring...\n");
		shutdown(socket_num,0);
		closesocket(socket_num);
		socket_num = -1;
	}
}

}
程序编译并下载到开发板，在 PC 上建立一个 tcp server，设置监听端口为 8080，IP地址为电脑本机的IP。

通过串口指令指定wifi的名称和密码，指定TCP服务器的IP地址和端口号。如：t-client("@snail","ss559550",8080,"192.168.2.103")

连接成功，网络调试助手会收到消息。