tcpserver select问题

发布于 2021-08-26 15:24:16 浏览：1274 订阅该版

```c
        while (is_running)
        {
            FD_ZERO(&readset_c);
            FD_SET(connected, &readset_c);

/* Wait for read or write */
            if (select(connected + 1, &readset_c, RT_NULL, RT_NULL, &timeout) == 0)
                continue;

/* 从connected socket中接收数据，接收buffer是1024大小，但并不一定能够收到1024大小的数据 */
            bytes_received = recv(connected, recv_data, BUFSZ, 0);
            if (bytes_received < 0)
            {
                LOG_E("Received error, close the connect.");
                closesocket(connected);
                connected = -1;
                break;
            }
            else if (bytes_received == 0)
            {
                /* 打印recv函数返回值为0的警告信息 */
                LOG_W("Received warning, recv function return 0.");
                continue;
            }
            else
            {
                /* 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 */
                    LOG_I("Got a 'q' or 'Q', close the connect.");
                    closesocket(connected);
                    connected = -1;
                    break;
                }
                else if (strcmp(recv_data, "exit") == 0)
                {
                    /* 如果接收的是exit，则关闭整个服务端 */
                    closesocket(connected);
                    connected = -1;
                    goto __exit;
                }
                else
                {
                    /* 在控制终端显示收到的数据 */
                    LOG_D("Received data = %s", recv_data);
                }
            }

/* 发送数据到connected socket */
            ret = send(connected, send_data, rt_strlen(send_data), 0);
            if (ret < 0)
            {
                LOG_E("send error, close the connect.");
                closesocket(connected);
                connected = -1;
                break;
            }
            else if (ret == 0)
            {
                /* 打印send函数返回值为0的警告信息 */
                LOG_W("Send warning, send function return 0.");
            }
        }
```
使用rt-thread范例tcpserver.c ，第一个select能按照指定时间超时，第二个select会立即返回，并不会阻塞，请问是怎么回事？ 版本rtt3.1.5

1 个回答

出出啊 2021-08-26

恃人不如自恃，人之为己者不如己之自为也

cris8259 2021-08-26

这家伙很懒，什么也没写！

代码没贴全
while (is_running)
    {
        FD_ZERO(&readset);
        FD_SET(sock, &readset);

LOG_I("Waiting for a new connection...");

/* Wait for read or write */
        if (select(sock + 1, &readset, RT_NULL, RT_NULL, &timeout) == 0)
            continue;

/* 接受一个客户端连接socket的请求，这个函数调用是阻塞式的 */
        connected = accept(sock, (struct sockaddr *)&client_addr, &sin_size);
        /* 返回的是连接成功的socket */
        if (connected < 0)
        {
            LOG_E("accept connection failed! errno = %d", errno);
            continue;
        }

/* 接受返回的client_addr指向了客户端的地址信息 */
        LOG_I("I got a connection from (%s , %d)\n",
                   inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));

/* 客户端连接的处理 */
        while (is_running)
        {
            FD_ZERO(&readset_c);
            FD_SET(connected, &readset_c);

/* Wait for read or write */
            if (select(connected + 1, &readset_c, RT_NULL, RT_NULL, &timeout) == 0)
                continue;

/* 从connected socket中接收数据，接收buffer是1024大小，但并不一定能够收到1024大小的数据 */
            bytes_received = recv(connected, recv_data, BUFSZ, 0);
            if (bytes_received < 0)
            {
                LOG_E("Received error, close the connect.");
                closesocket(connected);
                connected = -1;
                break;
            }
            else if (bytes_received == 0)
            {
                /* 打印recv函数返回值为0的警告信息 */
                LOG_W("Received warning, recv function return 0.");
                continue;
            }
            else
            {
                /* 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 */
                    LOG_I("Got a 'q' or 'Q', close the connect.");
                    closesocket(connected);
                    connected = -1;
                    break;
                }
                else if (strcmp(recv_data, "exit") == 0)
                {
                    /* 如果接收的是exit，则关闭整个服务端 */
                    closesocket(connected);
                    connected = -1;
                    goto __exit;
                }
                else
                {
                    /* 在控制终端显示收到的数据 */
                    LOG_D("Received data = %s", recv_data);
                }
            }

/* 发送数据到connected socket */
            ret = send(connected, send_data, rt_strlen(send_data), 0);
            if (ret < 0)
            {
                LOG_E("send error, close the connect.");
                closesocket(connected);
                connected = -1;
                break;
            }
            else if (ret == 0)
            {
                /* 打印send函数返回值为0的警告信息 */
                LOG_W("Send warning, send function return 0.");
            }
        }
    }