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在AP模式下实现TCP Server通信

前言

本文旨在探讨如何在AP模式下进行TCP Server通信。在AP模式下，模块可以作为一个softAP热点提供服务，当其他设备连接成功后，模块作为服务端等待客户端连接并进行通信。

理论基础

本节主要处理两个问题：如何利用RT_Thread连接路由器，以及如何使用Socket套接字编程实现TCP Server程序。

1. 连接路由器

模块需要开启station模式并连接到路由器。RT_Thread中，只需调用rt_wlan_set_mode和rt_wlan_start_ap函数即可实现。

rt_wlan_set_mode(RT_WLAN_DEVICE_AP_NAME, RT_WLAN_AP);
rt_wlan_start_ap("sand", "12345678");

2. Socket套接字实现TCP Server

服务端套接字使用流程以及和客户端交互框图如下所示（图片描述见附件）。

使用实例

1. 程序

程序位于w60x/applications/4-ap_tcp_server/main.c。以下是代码片段：

#include 
   
    
#include 
    
     
#include 
     
      
#define TCP_SERVER_ADDR "192.168.169.1"
#define TCP_SERVER_PORT 8089
static void tcp_client_thread_entry(void *args) {
    int ret = 0;
    int fd = (int) args;
    int len = 0;
    fd_set readfds;
    char buf[512] = {0};
    struct timeval t;
    t.tv_sec = 5;
    t.tv_usec = 0;
    while (1) {
        FD_ZERO(&readfds);
        FD_SET(fd, &readfds);
        ret = select(fd + 1, &readfds, NULL, NULL, &t);
        if ((ret > 0) && FD_ISSET(fd, &readfds)) {
            len = recv(fd, buf, sizeof(buf), 0);
            if (len > 0) {
                buf[len] = 0x00;
                rt_kprintf("receive data:%s\r\n", buf);
            } else {
                rt_kprintf("receive data from tcp server error!\r\n");
                goto exit;
            }
            if (-1 != fd) {
                rt_sprintf(buf, "%s\r\n", buf);
                ret = send(fd, buf, strlen(buf), 0);
                if (ret < 0) {
                    rt_kprintf("send error, close socket");
                    goto exit;
                }
            }
        }
    }
exit:
    if (-1 != fd) {
        closesocket(&fd);
        fd = -1;
    }
}
static void tcp_server_thread_entry(void *args) {
    int ret = 0;
    int fd = -1, client_fd = -1;
    struct sockaddr_in server_addr, client_addr;
    struct timeval t;
    fd_set readfds;
    socklen_t sockaddr_t_size;
    char buf[512] = {0};
    int len = 0;
reconnect:
    fd = socket(AF_INET, SOCK_STREAM, 0);
    if (-1 == fd) {
        rt_kprintf("create socket error!!!\r\n");
        goto exit;
    }
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(TCP_SERVER_PORT);
    server_addr.sin_addr.s_addr = INADDR_ANY;
    rt_memset(&server_addr.sin_zero, 0x00, sizeof(server_addr.sin_zero));
    ret = bind(fd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr));
    if (0 == ret) {
        rt_kprintf("bind success\r\n");
    } else {
        rt_kprintf("connect error!!!\r\n");
        goto try_reconnect;
    }
    ret = listen(fd, 5);
    if (-1 == ret) {
        rt_kprintf("Listen error\r\n");
        goto try_reconnect;
    }
    t.tv_sec = 2;
    t.tv_usec = 0;
    while (1) {
        FD_ZERO(&readfds);
        FD_SET(fd, &readfds);
        ret = select(fd + 1, &readfds, 0, 0, &t);
        if (-1 == ret) {
            rt_kprintf("select() error!\r\n");
            goto try_reconnect;
        } else if (ret > 0) {
            if (FD_ISSET(fd, &readfds)) {
                client_fd = accept(fd, (struct sockaddr *)&client_addr, &sockaddr_t_size);
                if (client_fd < 0) {
                    rt_kprintf("accept connection failed! errno = %d\n", errno);
                    continue;
                }
                rt_kprintf("client connected, ip:%s, port:%d", inet_ntoa(client_addr), ntohs(client_addr.sin_port));
                //create client thread
                rt_thread_t uart_thread = rt_thread_create("clients", tcp_client_thread_entry, client_fd, 4*1024, 25, 10);
                if (uart_thread != NULL) {
                    rt_thread_startup(uart_thread);
                } else {
                    ret = RT_ERROR;
                    rt_kprintf("create tcp client error!!!");
                    closesocket(fd);
                }
            }
        }
    }
try_reconnect:
    if (-1 != fd) {
        closesocket(fd);
    }
    rt_thread_sleep(1);
    goto reconnect;
exit:
    if (-1 != fd) {
        closesocket(fd);
    }
    rt_kprintf("thread server exit!\r\n");
}
int main(void) {
    rt_err_t ret = RT_EOK;
    char str[] = "hello world!\r\n";
    rt_wlan_set_mode(RT_WLAN_DEVICE_AP_NAME, RT_WLAN_AP);
    rt_wlan_start_ap("sand", "12345678");
    rt_thread_t uart_thread = rt_thread_create("server", tcp_server_thread_entry, RT_NULL, 4*1024, 25, 10);
    if (uart_thread != NULL) {
        rt_thread_startup(uart_thread);
    } else {
        ret = RT_ERROR;
        rt_kprintf("create tcp client error!!!");
    }
exit:
    return ret;
}
     
    
   

2. 目标文件配置

默认的SConscript脚本需要修改以支持4-ap_tcp_server项目。修改后的脚本如下：

Import('RTT_ROOT')
Import('rtconfig')
from building import *
cwd = GetCurrentDir()
src = Glob('4-ap_tcp_server/main.c')
CPPPATH = [cwd]
group = DefineGroup('Applications', src, depend=[''], CPPPATH = CPPPATH)
Return('group')

下载运行

在ENV控制台中，输入scons命令生成build/Bin/rtthread_1M.FLS文件。烧录运行后，连接模块的热点，使用网络助手配置两个TCP客户端，设置目标IP和端口为192.168.169.1:8089。通过发送数据测试通信功能。

结语

总结

实际操作中需注意以下几点：

资料获取

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