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测试Winsock的select

news 2025/7/15 4:51:04

说明

实现了一个回显一行字符串的服务器：客户端发送一行字符串，一’\n’结尾，服务器接受完一行后就原封不动地发回给客户端。
windows下对select的能监控的Socket数量是有限制的，若超过，一种方案是再开一个线程。

#ifndef FD_SETSIZE
#define FD_SETSIZE      64
#endif /* FD_SETSIZE */

代码

#include <iostream>
#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <WinSock2.h>
#include <vector>
#include <memory>#pragma comment(lib, "Ws2_32.lib")struct ClientSocketItem
{ClientSocketItem(){hSocket = NULL;memset(szRecv, 0, sizeof(szRecv));nRecvSize = 0;bNeedWrite = false;nWriteOffset = 0;}SOCKET hSocket;char szRecv[1024];unsigned int nRecvSize;std::string strIp;bool bNeedWrite;//接受完成，可以发送unsigned int nWriteOffset = 0;
};std::vector<std::shared_ptr<ClientSocketItem>> g_Clients;void do_accept(SOCKET hListenSocket)
{sockaddr_in mPeerAddr = { 0 };int nAddrLen = sizeof(sockaddr);SOCKET hClientSocket = accept(hListenSocket, (sockaddr*)(&mPeerAddr), &nAddrLen);if (INVALID_SOCKET == hClientSocket){std::cout << "accept failed with error "<< WSAGetLastError() << std::endl;}else{unsigned long nNoBlock = 0;ioctlsocket(hClientSocket, FIONBIO, &nNoBlock);std::string strIpAddr = inet_ntoa(mPeerAddr.sin_addr);std::cout << "accept success, peer ip is " << strIpAddr.c_str() << std::endl;auto pClient = std::make_shared<ClientSocketItem>();pClient->hSocket = hClientSocket;pClient->strIp = strIpAddr;g_Clients.push_back(pClient);}
}bool do_read(const std::shared_ptr<ClientSocketItem>& pClient )
{if (!pClient){return false;}char c = 0; //测试用，每次只读一个字符int nRecvValue = recv(pClient->hSocket, &c, 1, 0);if (nRecvValue > 0){pClient->szRecv[pClient->nRecvSize] = c;pClient->nRecvSize += 1;std::cout << "read one char: " << c << std::endl;if (c == '\n'){std::cout << "read finished" << std::endl;pClient->bNeedWrite = true;}return true;}else if (0 == nRecvValue){std::cout << "peer client closed" << std::endl;closesocket(pClient->hSocket);return false;}else{int nError = WSAGetLastError();if (WSAEWOULDBLOCK != nError){std::cerr << "recv failed with error " << nError << std::endl;closesocket(pClient->hSocket);return false;}std::cout << "next recv" << std::endl;return true;}
}bool do_write(const std::shared_ptr<ClientSocketItem>& pClient)
{if (!pClient){return false;}if (!pClient->bNeedWrite){return true;}//测试用，每次只发送一个字符int nRet = send(pClient->hSocket, pClient->szRecv + pClient->nWriteOffset, 1, 0);if (nRet >= 0){std::cout << "send one char: " << pClient->szRecv[pClient->nWriteOffset] << std::endl;pClient->nWriteOffset += 1;if (pClient->nWriteOffset == pClient->nRecvSize){std::cout << "send finished, close client(" << pClient->strIp.c_str()<< ")" << std::endl;pClient->bNeedWrite = false;closesocket(pClient->hSocket);return false;}return true;}else{int nError = WSAGetLastError();if (WSAEWOULDBLOCK != nError){std::cerr << "send failed with error " << nError << std::endl;closesocket(pClient->hSocket);return false;}std::cout << "next send" << std::endl;return true;}
}int main(int argc, char* argv)
{WORD wVersionRequested = MAKEWORD(2, 2);WSADATA wsaData = { 0 };int err = WSAStartup(wVersionRequested, &wsaData);if (err != 0){return -1;}if (LOBYTE(wsaData.wVersion) != 2 ||HIBYTE(wsaData.wVersion) != 2){WSACleanup();return -1;}SOCKET hListenSocket = socket(AF_INET, SOCK_STREAM, 0);if (INVALID_SOCKET == hListenSocket){std::cerr << "create socket failed with error " << WSAGetLastError()<< std::endl;return -1;}sockaddr_in mSockAddrIn = { 0 };mSockAddrIn.sin_family = AF_INET;mSockAddrIn.sin_port = htons((u_short)8878);mSockAddrIn.sin_addr.S_un.S_addr = inet_addr("0.0.0.0");if (SOCKET_ERROR == bind(hListenSocket, (sockaddr*)(&mSockAddrIn),sizeof(sockaddr))){std::cerr << "bind failed with error " << WSAGetLastError() << std::endl;return -1;}if (SOCKET_ERROR == listen(hListenSocket, SOMAXCONN)){std::cerr << "listen failed with error " << WSAGetLastError() << std::endl;return -1;}std::vector<SOCKET> mAllClients;while (true){fd_set readfds;fd_set writefds;fd_set exceptfds;FD_ZERO(&readfds);FD_ZERO(&writefds);FD_ZERO(&exceptfds);FD_SET(hListenSocket, &readfds);//FD_SET(hListenSocket, &writefds);//FD_SET(hListenSocket, &exceptfds);for (auto it = g_Clients.begin(); it != g_Clients.end(); ++it){std::shared_ptr<ClientSocketItem> pClientItem = *it;if (!pClientItem) continue;FD_SET(pClientItem->hSocket, &readfds);if (pClientItem->bNeedWrite)//否则select会一直有事件{FD_SET(pClientItem->hSocket, &writefds);}FD_SET(pClientItem->hSocket, &exceptfds);}int nRet = select(0, &readfds, &writefds, &exceptfds, nullptr);std::cout << "select return with " << nRet << std::endl;if (nRet > 0){//readif (FD_ISSET(hListenSocket, &readfds)){do_accept(hListenSocket);}for (auto it = g_Clients.begin(); it != g_Clients.end();){std::shared_ptr<ClientSocketItem> pClientItem = *it;if (pClientItem && FD_ISSET(pClientItem->hSocket, &readfds)){if (!do_read(pClientItem)){it = g_Clients.erase(it);continue;}}++it;}//writefor (auto it = g_Clients.begin(); it != g_Clients.end();){std::shared_ptr<ClientSocketItem> pClientItem = *it;if (pClientItem && FD_ISSET(pClientItem->hSocket, &writefds)){if (!do_write(pClientItem)){it = g_Clients.erase(it);continue;}}++it;}//end of for//error for (auto it = g_Clients.begin(); it != g_Clients.end();){std::shared_ptr<ClientSocketItem> pClientItem = *it;if (pClientItem && FD_ISSET(pClientItem->hSocket, &exceptfds)){std::cerr << "client socket except, close and remove it" << std::endl;closesocket(pClientItem->hSocket);it = g_Clients.erase(it);continue;}++it;}//end of for}else{std::cerr << "select failed with error " << WSAGetLastError() << std::endl;}}return 0;
}