这个功能反反复复折腾了好几天，多亏开鸿智谷原厂工程师支持。

一、目标

基于LWIP，在NiobeU4开发板上部署TCP Client，连接测试服务器，获取服务器发来的信息。

二、设计实现

（一）TCP Server

Server直接在计算机上，用Python实现了个简单的，功能就是client连接上后，给其发送一段字符。

import socket

# 指定协议
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# 让端口可以重复使用
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
# 绑定ip和端口
server.bind(('0.0.0.0', 8080))
# 监听
server.listen(1)
# 等待消息
while1:
  clientsocket, address = server.accept()
  clientsocket.send(address[0].encode("utf-8")+b'HELLO world~')
  clientsocket.close()
server.close()

代码比较简单，读读也清晰。

（二）TCP Client

开发板端实现TCP Client功能即可，如上图，首先创建socket，再connect server，然后send 数据，最后close socket，一个典型的TCP Server-Client案例就好了，这次Client不发送而是接收（recv）信息，得益于OpenHarmony的LWIP协议栈，Client实现跟Linux编程毫无区别，具体代码如下：

void wifi_test(void)
{
    int sock = -1;
    struct sockaddr_in client_addr;
    char recv_data[768] = {0};
    int recv_data_len;
    WifiConnect(WIFI_NAME, WIFI_PWD);
    while (1) {
        sock = socket(AF_INET, SOCK_STREAM, 0);
        if (sock < 0) {
            printf("Socket error\n");
            osDelay(OD_DELAY_100);
            continue;
        }
        memset_s(&(client_addr), sizeof(client_addr), 0, sizeof(client_addr));
        client_addr.sin_family = AF_INET;
        client_addr.sin_port = htons(SERVER_PORT);
        client_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
        printf("try connect to server "SERVER_IP" :%d \n", SERVER_PORT);
        if (connect(sock, (struct sockaddr *)&client_addr, sizeof(struct sockaddr)) == -1) {
            closesocket(sock);
            osDelay(OD_DELAY_1000);
            continue;
        }
        printf("Connect to tcp server successful!\n");		
        while (1) {
            recv_data_len = recv(sock, recv_data, RECV_LEN, 0);
            if (recv_data_len <= 0) {
                break;
            } else {
                recv_data[recv_data_len] = '\0';
            }
            printf("recv: %s\n", recv_data);
            write(sock, recv_data, recv_data_len);
        }
        close(sock);
	break;
    }
}

三、编译烧录

反正hb set，hb build -f一顿操作猛如虎，直接烧写OHOS Img即可，其他的bootloader和partition因为没有变化，不必重新烧录。

四、运行

从系统log中，可以看出，NiobeU4板子启动后收到了Server发来的数据，HELLO world~。

[20:07:45:841]<--System Init-->
[20:07:45:841]<--Wifi Init-->
[20:07:45:841]register wifi event succeed!
[20:07:45:841]I (161) wifi_init: WiFi RX IRAM OP enabled
[20:07:45:992]I (558) phy_init: phy_version 4670,719f9f6,Feb 18 2021,17:07:07
[20:07:45:992]I (2378) wifi:mode : 
[20:07:48:981]WaitScanResult:wait success[3]s
[20:07:48:981]starlink  
[20:07:48:981]
[20:07:49:835]sta (44:17:93:96:e6:34)
[20:07:49:835]I (2378) wifi:enable tsf
[20:07:49:835]I (6228) wifi:new:<8,0>, old:<1,0>, ap:<255,255>, sta:<8,0>, prof:1
[20:07:49:841]I (6228) wifi:state: init -> auth (b0)
[20:07:49:866]I (6238) wifi:state: auth -> assoc (0)
[20:07:49:866]I (6248) wifi:state: assoc -> run (10)
[20:07:49:866]I (6248) wifi:connected with starlink, aid = 6, channel 8, BW20, bssid = 3e:87:46:16:13:6e
[20:07:49:880]I (6248) wifi:security: Open Auth, phy: bgn, rssi: -50
[20:07:49:880]I (6callback function for wifi connect
[20:07:49:880]248) wifi:pm start, type: 1
[20:07:49:954]
[20:07:49:954]W (6268) wifi:<ba-add>idx:0 (ifx:0, 3e:87:46:16:13:6e), tid:0, ssn:0, winSize:64
[20:07:49:969]I (6348) wifi:AP's
[20:07:52:482]WaitConnectResult:wait success[1]s
[20:07:52:482]WiFi connect succeed!
[20:07:52:482]
[20:07:53:485]start wifi_test test
[20:07:53:485]try connect to server 192.168.43.159 :8080 
[20:07:53:485]Connect to tcp server successful!
[20:07:53:495]recv: 192.168.43.158HELLO world~
[20:07:53:505]try connect to server 192.168.43.159 :8080 
[20:07:53:505]Connect to tcp server successful!
[20:07:53:509]recv: 192.168.43.158HELLO world~
[20:07:53:523]try connect to server 192.168.43.159 :8080 
[20:07:53:523]Connect to tcp server successful!
[20:07:53:523]recv: 192.168.43.158HELLO world~

##感谢阅读##