C++ TCP/IP 关于tcp断线重连的问题-编程学习网

在工控上经常用到tcp连接，比如串口服务器或某些支持modbustcp协议的仪表等，以前尽量使用串口服务器的虚拟串口功能，现在逐步使用上了tcpserver或tcpclient模式。

搜索了个C++ 的tcp断线重连的案例（http://www.cnblogs.com/kingdom_0/articles/2571727.html），使用这个的原因还因其使用的是收发多线程。server和client都很全，也许是作者的疏忽，client出现了明显的bug。如果掉线了，client的send和recv将重新建两个socket。

所以send和recv两个线程中的socket必须以指针形式传入，其次关闭socket不能用shutdown。经改进，目前已实现比较完美的断线（断开服务器程序和拔掉网线方式测试）自动连接功能。

完整client代码cpp文件如下：

include #include #include #include #include #include #include #pragma comment(lib,"Ws2_32.lib")using namespace std;#define PORT 6100#define IP_ADDRESS "127.0.0.1"#include "ClientTcp.h"#include "ThreadLock.h"//线程自动锁 ThreadLock.h WSADATA  Ws;SOCKET ClientSocket;struct sockaddr_in ServerAddr;int Ret = 0;HANDLE hSendThread = NULL;HANDLE hRevcThread = NULL;//发送消息结构体struct SendMsgStruct{    SOCKET* clientSocket;    string msg;    struct sockaddr_in ServerAddr;};//接收消息结构体struct RecvMsgStruct{    SOCKET* clientSocket;    struct sockaddr_in ServerAddr;};DWORD WINAPI SendThread(LPVOID lpParameter);//发送消息子线程DWORD WINAPI RecvThread(LPVOID lpParameter);//接收消息子线程ClientTcp::ClientTcp(std::string strIp, unsigned int uPort) :    m_strIp(strIp),    m_uPort(uPort){}ClientTcp::~ClientTcp(){       if (ClientSocket)       {           closesocket(ClientSocket);           ClientSocket = NULL;       }}bool ClientTcp::InitClient(){    //初始化 Windows Socket    if (WSAStartup(MAKEWORD(2, 2), &Ws) != 0)    {       std::cout << "初始化 Socket 失败:" << GetLastError() << endl;        return -1;    }    //创建 Socket    ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);    if (ClientSocket == INVALID_SOCKET)    {        cout << "创建 Socket 失败:" << GetLastError() << endl;        return -1;    }    ServerAddr.sin_family = AF_INET;    ServerAddr.sin_addr.s_addr = inet_addr(IP_ADDRESS);    ServerAddr.sin_port = htons(PORT);    //设置ServerAddr中前8个字符为0x00    memset(ServerAddr.sin_zero, 0x00, 8);    Ret = connect(ClientSocket, (struct sockaddr*)&ServerAddr, sizeof(ServerAddr));    if (Ret == SOCKET_ERROR)    {        cout << "建立连接过程发生错误:" << GetLastError() << endl;    }    else    {        cout << "连接建立成功" << endl;    }    //创建一个子线程，用于向服务器端发送消息    struct SendMsgStruct* msgSend = new struct SendMsgStruct();    msgSend->clientSocket = &ClientSocket;    msgSend->msg = "你好,Msg From Client";    msgSend->ServerAddr = ServerAddr;    //传递一个struct    hSendThread = CreateThread(NULL, 0, SendThread, (LPVOID)msgSend, 0, NULL);    //WaitForSingleObject(hSendThread, INFINITE);    if (hSendThread == NULL)    {        cout << "创建发送消息子线程失败" << endl;        system("pause");        return -1;    }    //创建一个子线程，用于接收从服务器端发送过来的消息    struct RecvMsgStruct* msgRecv = new struct RecvMsgStruct();    msgRecv->clientSocket = &ClientSocket;    msgRecv->ServerAddr = ServerAddr;    //传递一个struct指针参数    hRevcThread = CreateThread(NULL, 0, RecvThread, (LPVOID)msgRecv, 0, NULL);    //WaitForSingleObject(hRevcThread, INFINITE);    if (hRevcThread == NULL)    {        cout << "创建接收消息子线程失败" << endl;        system("pause");        return -1;    }    //客户端输入exit，退出       closesocket(ClientSocket);    WSACleanup();}//发送消息子线程DWORD WINAPI SendThread(LPVOID lpParameter){    SendMsgStruct* myStruct = (SendMsgStruct*)lpParameter;    SOCKET* ClientSocket = myStruct->clientSocket;    string SendMsg = myStruct->msg;    struct sockaddr_in ServerAddr = myStruct->ServerAddr;    while (true)    {        int flag = 0;        int bufSize = SendMsg.length();        char* buf = const_cast(SendMsg.c_str());        {            CAutoLock ALock(&ctLock);            flag = send(*ClientSocket, buf, bufSize, 0);            //判断当前时候存在可用连接,如果没有，再次连接            while (flag == SOCKET_ERROR || flag == 0)            {                cout << "准备重连" << endl;                closesocket(*ClientSocket);                *ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);                if (connect(*ClientSocket, (struct sockaddr*)&ServerAddr, sizeof(ServerAddr)) == SOCKET_ERROR)                {                    cout << "重连失败 :" << GetLastError() << endl;                    Sleep(5000);                }                else                {                    break;                }            }            if (flag < bufSize)            {                flag = send(*ClientSocket, buf, bufSize - flag, 0);            }            else    //传输成功            {                cout << "\n消息传输成功" << endl;            }        }        Sleep(2000);       //每2秒发送一次    }    return 0;}//接收消息子线程DWORD WINAPI RecvThread(LPVOID lpParameter){    RecvMsgStruct* recvStruct = (RecvMsgStruct*)lpParameter;    SOCKET* ClientSocket = recvStruct->clientSocket;    struct sockaddr_in ServerAddr = recvStruct->ServerAddr;    while (true)    {        char recvBuf[500] = { "0" };        int byteRecv = recv(*ClientSocket, recvBuf, 500, 0);        CAutoLock ALock(&ctLock);        int connectState;        while (byteRecv == 0 || byteRecv == SOCKET_ERROR)        {            //连接断开，重连            cout << "byteRecv <= 0" << endl;             closesocket(*ClientSocket);            *ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);            connectState = connect(*ClientSocket, (struct sockaddr*)&ServerAddr, sizeof(ServerAddr));            if (connectState == SOCKET_ERROR)            {                cout << "建立连接发生错误,错误代码:" << GetLastError() << endl;            }            else            {                cout << "重连成功!!!!!!!" << endl;                break;            }            Sleep(5000);        }        cout << recvBuf << endl;    }    return 0;}

H头文件中代码如下：

#pragma once#include #include #include #pragma comment(lib,"ws2_32")//Standard socket API.#include "sendByte.h"//发送属性实体（根据需求自定义变量即可）#include "TcpDatas.h"//接收属性实体（根据需求自定义变量即可）#include "Totype.h"//类型转化函数类class ClientTcp{public:    ClientTcp(std::string strIp, unsigned int uPort);    virtual ~ClientTcp();    //初始化网络服务端    bool InitClient(); private:    unsigned int m_uPort;//监听端口    std::string m_strIp;//用于监听本机指定IP地址  };

入口文件中调用：

void TcpClientRun(){    ClientTcp clienttcp("192.168.124.3", 6100);    if (!clienttcp.InitClient())    {        getchar();    }}int main(int argc, char* argv[]){    std::thread CTcpTh(TcpClientRun);    this_thread::sleep_for(std::chrono::milliseconds(1000));    CTcpTh.join();    return 0;  }

这样就可以了

线程自动锁 ThreadLock.h 选用https://www.cnblogs.com/pilipalajun/p/5415673.html；

本文主要参考原文链接：https://blog.csdn.net/gongzhu110/article/details/83147994

来源地址：https://blog.csdn.net/qiuyuanxiang1230/article/details/130487710

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