rt-thread-official/examples/network/tcpclient.c

#include <rtthread.h>

#include <lwip/netdb.h>   /* 为了解析主机名，需要包含netdb.h头文件 */
#include <lwip/sockets.h> /* 使用BSD socket，需要包含sockets.h头文件 */

#define BUFSZ   1024

static const char send_data[] = "This is TCP Client from RT-Thread."; /* 发送用到的数据 */
void tcpclient(const char* url, int port)
{
    int ret;
    char *recv_data;
    struct hostent *host;
    int sock, bytes_received;
    struct sockaddr_in server_addr;

    /* 通过函数入口参数url获得host地址（如果是域名，会做域名解析） */
    host = gethostbyname(url);

    /* 分配用于存放接收数据的缓冲 */
    recv_data = rt_malloc(BUFSZ);
    if (recv_data == RT_NULL)
    {
        rt_kprintf("No memory\n");
        return;
    }

    /* 创建一个socket，类型是SOCKET_STREAM，TCP类型 */
    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        /* 创建socket失败 */
        rt_kprintf("Socket error\n");

        /* 释放接收缓冲 */
        rt_free(recv_data);
        return;
    }

    /* 初始化预连接的服务端地址 */
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    server_addr.sin_addr = *((struct in_addr *)host->h_addr);
    rt_memset(&(server_addr.sin_zero), 0, sizeof(server_addr.sin_zero));

    /* 连接到服务端 */
    if (connect(sock, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1)
    {
        /* 连接失败 */
        rt_kprintf("Connect fail!\n");
        lwip_close(sock);

        /*释放接收缓冲 */
        rt_free(recv_data);
        return;
    }

    while(1)
    {
        /* 从sock连接中接收最大BUFSZ - 1字节数据 */
        bytes_received = recv(sock, recv_data, BUFSZ - 1, 0);
        if (bytes_received < 0)
        {
            /* 接收失败，关闭这个连接 */
            lwip_close(sock);
            rt_kprintf("\nreceived error,close the socket.\r\n");

            /* 释放接收缓冲 */
            rt_free(recv_data);
            break;
        }
        else if (bytes_received == 0)
        {
            /* 打印recv函数返回值为0的警告信息 */
            rt_kprintf("\nReceived warning,recv function return 0.\r\n");
            continue;
        }

        /* 有接收到数据，把末端清零 */
        recv_data[bytes_received] = '\0';

        if (strcmp(recv_data , "q") == 0 || strcmp(recv_data , "Q") == 0)
        {
            /* 如果是首字母是q或Q，关闭这个连接 */
            lwip_close(sock);
            rt_kprintf("\n got a 'q' or 'Q',close the socket.\r\n");

            /* 释放接收缓冲 */
            rt_free(recv_data);
            break;
        }
        else
        {
            /* 在控制终端显示收到的数据 */
            rt_kprintf("\nReceived data = %s " , recv_data);
        }

        /* 发送数据到sock连接 */
        ret = send(sock,send_data,strlen(send_data), 0);
        if (ret < 0)
        {
            /* 接收失败，关闭这个连接 */
            lwip_close(sock);
            rt_kprintf("\nsend error,close the socket.\r\n");

            rt_free(recv_data);
            break;
        }
        else if (ret == 0)
        {
            /* 打印send函数返回值为0的警告信息 */
            rt_kprintf("\n Send warning,send function return 0.\r\n");
        }
    }

    return;
}

#ifdef RT_USING_FINSH
#include <finsh.h>
/* 输出tcpclient函数到finsh shell中 */
FINSH_FUNCTION_EXPORT(tcpclient, startup tcp client);
#endif