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 <iostream>
#include <Winsock2.h>
#include <Windows.h>
#include <fstream>
#include <map>
#include <string>
#include <sstream>
#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
/* string clientString;
do
{
getline(cin, clientString);
} while (clientString != "exit" && clientString != "EXIT");*/
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<char*>(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 <string>
#include <winsock2.h>
#include <thread>
#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；文章来源：https://www.toymoban.com/news/detail-693302.html
本文主要参考原文链接：https://blog.csdn.net/gongzhu110/article/details/83147994文章来源地址https://www.toymoban.com/news/detail-693302.html
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