用C++ Thread实现简单的socket多线程通信

起因

为什么要用C++的Thread，很简单，因为我菜

一打五用pthread实现了socket多线程通信，我之前学并发的时候没看pthread，因此代码只能看个大概，后面还是要系统学一下pthread的

服务端

多线程功能放在腾讯云服务器上，代码如下：

#include "tcpserver.h"
#include <thread>
#include <mutex>

TcpServer server;
mutex tcp_mutex;

void tcpFunc(int clientfd);

int main(int argc, char *argv[])
{

    if (server.initServer(6666) == false)
    {
        cout << "服务端初始化失败！！!" << endl;
        return -1;
    }

    vector<thread> tcp_vec;
    while (true)
    {
        if (!server.tcpAccept())
        {
            continue;
        }
        tcp_vec.emplace_back(tcpFunc, server.m_connectfd);
        // thread tcpThread(tcpFunc, server.m_connectfd);
        // if (tcpThread.joinable())
        if(tcp_vec.back().joinable())
        {
            // cout << "Tcp thread " << tcpThread.get_id() << "is joinable!" << endl;
            cout << "Tcp thread " << tcp_vec.back().get_id() << " is joinable!" << endl;
            tcp_vec.back().detach();
        }
    }

    return 0;
}

void tcpFunc(int clientfd)
{
    int buf_len = 0;
    char buffer[1024];
    while (true)
    {
        unique_lock<mutex> tcplck(tcp_mutex);
        memset(buffer, 0, sizeof(buffer));
        if (!server.tcpRecv(clientfd, buffer, &buf_len, 5))
        {
            cout << "接收客户端数据失败！" << endl;
            tcplck.unlock();
            break;
        }
        cout << "服务端接收数据:" << buffer << endl;

        strcpy(buffer, "I am your father!");
        if (!server.tcpSend(clientfd, buffer, sizeof(buffer)))
        {
            cout << "向客户端发送数据失败！" << endl;
            tcplck.unlock();
            break;
        }
        tcplck.unlock();
				usleep(100);
    }
    cout << "通信异常！" << endl;
    return;
}
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实在是很简单，贻笑大方了

有几个注意点：

• 全局变量在main函数执行完后会销毁，线程中用到了全局变量server，线程detach后要保证数据的收发，就要保持server的生存期，这里体现为在main中循环等待客户端的连接
• 要用锁锁住线程中server的操作，避免不同线程同时操作server造成混乱
• usleep(100);是为了避免不同线程争抢同一把锁而造成死锁的发生

ROS客户端

#include "tcpclient.h"
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>

TcpClient client;
string send_str = "I am king of the world!";
char recv_buff[1024];

void client_callback(const geometry_msgs::Twist::ConstPtr &msg)
{
    cout << "vel X:" << msg->linear.x << ";vel Y:" << msg->linear.y << ";angular Z:" << msg->angular.z << endl;
    if (!client.tcpSend(client.m_sockfd, send_str.data(), send_str.size()))
    {
        cout << "向服务端发送报文失败！" << endl;
    }
    if (!client.tcpRecv(client.m_sockfd, recv_buff, NULL, 10))
    {
        cout << "从服务端接收报文失败！" << endl;
    }
    cout << "接收服务端报文：" << recv_buff << endl << endl;
}

int main(int argc, char **argv)
{
    ros::init(argc, argv, "joystick_client");
    ros::NodeHandle nh;

    string server_ip = "1.116.137.21";
    string loop_ip = "127.0.0.1";

    if (client.connectToServer(server_ip.data(), 6666) == false)
    {
        cout << "连接失败！！！" << endl;
        return -1;
    }

    ros::Subscriber sub = nh.subscribe("/cmd_vel", 1, client_callback);

    ros::spin();
}
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很简单，订阅了手柄发布的话题/cmd_vel，在回调函数中和服务端通讯

话题的发布频率是10Hz，意味着和服务端通讯的频率也是10Hz

普通客户端

#include "tcp/tcpclient.h"

int main(int argc, char **argv)
{
    TcpClient client;

    string server_ip = "1.116.137.21";
    string loop_ip = "127.0.0.1";

    if (client.connectToServer(server_ip.data(), 6666) == false)
    {
        cout << "连接失败！！！" << endl;
        return -1;
    }
    cout << "成功连接服务器！" << endl;

    char buff[1024];
    while (true)
    {
        memset(buff, 0, sizeof(buff));
        sprintf(buff, "Ouch!");
        if (!client.tcpSend(client.m_sockfd, buff, sizeof(buff)))
        {
            cout << "向服务端发送报文失败！" << endl;
            return -1;
        }

        memset(buff, 0, sizeof(buff));
        if (!client.tcpRecv(client.m_sockfd, buff, NULL, 5))
        {
            cout << "从服务端接收报文失败！" << endl;
            return -1;
        }
        cout << "接收服务端报文：" << buff << endl << endl;
        sleep(0.1);
    }
    return 0;
}
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这里sleep(0.1);是为了模拟ROS中话题的频率

sleep过长会导致服务端阻塞等待该客户端的消息，从而导致其余客户端与服务端的通信失败(如果客户端中允许的通信延时很短的话)

运行效果

云服务器上的服务端

[root@VM-4-11-centos bin]# ./server_thread 
Tcp thread 140662362572544 is joinable!
服务端接收数据:I am king of the world!
服务端接收数据:I am king of the world!
服务端接收数据:I am king of the world!
服务端接收数据:I am king of the world!
Tcp thread 140662354179840 is joinable!
服务端接收数据:I am king of the world!
服务端接收数据:Ouch!
服务端接收数据:I am king of the world!
服务端接收数据:Ouch!
服务端接收数据:I am king of the world!
服务端接收数据:Ouch!
服务端接收数据:I am king of the world!
服务端接收数据:Ouch!
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笔记本上的ROS客户端

redwall@redwall-G3-3500:~$ rosrun joystick_client joystick_client 
[ERROR] [1656939307.244367879]: [registerPublisher] Failed to contact master at [localhost:11311].  Retrying...
[ INFO] [1656939314.923909682]: Connected to master at [localhost:11311]
vel X:0;vel Y:0;angular Z:0
接收服务端报文：I am your father!

vel X:0;vel Y:0;angular Z:0
接收服务端报文：I am your father!

vel X:0;vel Y:0;angular Z:0
接收服务端报文：I am your father!
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虚拟机的普通客户端

prejudice@prejudice-VirtualBox:~/socket_test/socket_for_linux/bin$ ./tcp_client 成功连接服务器！
接收服务端报文：I am your father!

接收服务端报文：I am your father!

接收服务端报文：I am your father!
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不足

1. 未考虑线程的清理
2. 未考虑信号的退出处理