14.4 Socket 双向数据通信

所谓双向数据传输指的是客户端与服务端之间可以无差异的实现数据交互，此类功能实现的核心原理是通过创建CreateThread()函数多线程分别接收和发送数据包，这样一旦套接字被建立则两者都可以异步发送消息，本章将实现简单的双向交互功能。

首先我们需要封装两个函数，这里RecvFunction函数用于接收数据，SendFunction函数则用于发送数据，这两段代码在服务端与客户端之间是一致的两者可被共用。

#include <iostream>
#include <Winsock2.h>　
#include <windows.h>
#pragma comment (lib, "ws2_32")
#define BUF_SIZE 6400// 接收数据线程
DWORD WINAPI RecvFunction(LPVOID lpParam)
{SOCKET sClient = *(SOCKET*)lpParam;int retVal;char bufRecv[BUF_SIZE];memset(bufRecv, 0, sizeof(bufRecv));while (1){retVal = recv(sClient, bufRecv, BUF_SIZE, 0);if (retVal == SOCKET_ERROR){printf("返回错误 \n");break;}else{printf("收到服务器消息: %s \n", bufRecv);}}return 0;
}// 发送数据线程
DWORD WINAPI SendFunction(LPVOID lpParam)
{SOCKET sClient = *(SOCKET*)lpParam;int retVal;char bufSend[BUF_SIZE];memset(bufSend, 0, sizeof(bufSend));while (1){gets_s(bufSend);retVal = send(sClient, bufSend, strlen(bufSend) + sizeof(char), 0);if (retVal == SOCKET_ERROR){printf("发送错误 \n");break;}}return 0;
}

14.4.1 服务端实现

对于服务端代码而言，一旦accept函数接收到有客户端连接后则自动将该sClient指针传输到子线程内执行，这样即可实现两者功能互不干扰。程序中通过使用CreateThread函数创建了两个线程来处理与客户端之间的发送和接收数据。将SendFunction和RecvFunction作为参数传递给线程，并与新的客户端套接字一起传递。线程存储在变量hThread1和hThread2中。

int main(int argc, char* argv[])
{// 初始化套接字动态库WSADATA wsaData;if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0){return 1;}//  创建服务段套接字SOCKET sServer = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);if (sServer == INVALID_SOCKET){WSACleanup();return -1;}//  服务端地址sockaddr_in addrServ;addrServ.sin_family = AF_INET;addrServ.sin_port = htons(9999);addrServ.sin_addr.s_addr = htonl(INADDR_ANY);//  绑定套接字if (bind(sServer, (const struct sockaddr*)&addrServ, sizeof(addrServ)) == SOCKET_ERROR){closesocket(sServer);WSACleanup();return -1;}//  监听套接字if (listen(sServer, 5) == SOCKET_ERROR){closesocket(sServer);WSACleanup();return -1;}SOCKET sClient;sockaddr_in addrClient;int addrClientLen = sizeof(addrClient);// 接收数据sClient = accept(sServer, (sockaddr FAR*) & addrClient, &addrClientLen);if (sClient == INVALID_SOCKET){closesocket(sServer);WSACleanup();return -1;}printf("接收客户端 IP:[%s] --> port:[%d] \n", inet_ntoa(addrClient.sin_addr), ntohs(addrClient.sin_port));// 分配线程HANDLE hThread1, hThread2;hThread1 = CreateThread(NULL, NULL, SendFunction, (LPVOID*)&sClient, 0, 0);hThread2 = CreateThread(NULL, NULL, RecvFunction, (LPVOID*)&sClient, 0, 0);WaitForSingleObject(hThread1, INFINITE);WaitForSingleObject(hThread2, INFINITE);CloseHandle(hThread1);CloseHandle(hThread2);closesocket(sClient);WSACleanup();return 0;
}

14.4.2 客户端实现

客户端的实现与服务端保持一致，唯一的区别在于客户端通过connect()主动向服务端发送连接请求，只要有新的连接被建立则将通过CreateThread函数创建线程，SendFunction与RecvFunction函数分别用于发送与接收功能。

int main(int argc, char* argv[])
{WSADATA wsaData;// 初始化库if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0){return 1;}//  服务器套接字SOCKET sHost = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);if (sHost == INVALID_SOCKET){WSACleanup();return -1;}SOCKADDR_IN servAddr;servAddr.sin_family = AF_INET;servAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");servAddr.sin_port = htons(9999);//  连接服务器if (connect(sHost, (LPSOCKADDR)&servAddr, sizeof(servAddr)) == SOCKET_ERROR){closesocket(sHost);WSACleanup();return -1;}printf("连接到服务器 IP:[%s] --> port:[%d] \n", inet_ntoa(servAddr.sin_addr), ntohs(servAddr.sin_port));// 分别创建两个线程HANDLE hThread1, hThread2;hThread1 = CreateThread(NULL, NULL, SendFunction, (LPVOID)&sHost, 0, 0);hThread2 = CreateThread(NULL, NULL, RecvFunction, (LPVOID)&sHost, 0, 0);WaitForSingleObject(hThread1, INFINITE);WaitForSingleObject(hThread2, INFINITE);CloseHandle(hThread1);CloseHandle(hThread2);closesocket(sHost);WSACleanup();return 0;
}