c++下基于windows socket的单线程服务器客户端程序(基于TCP协议)

今天自己编写了一个简单的c++服务器客户端程序，注释较详细，在此做个笔记。

windows下socket编程的主要流程可概括如下：初始化ws2_32.dll动态库-->创建套接字-->绑定地址信息-->服务器进行监听/客户端连接服务器-->数据交换-->关闭套接字对象。

服务器端：

 #include <Winsock2.h>
 #include <Ws2tcpip.h>
 #include <iostream>

 #pragma comment(lib, "ws2_32.lib") //socket编程需要引用该库

 using std::cerr;
 using std::cout;
 using std::endl;

 const char DEFAULT_PORT[] = "";
 const int RECV_BUF_SIZE = ;
 const size_t IP_BUF_SIZE = ;

 //服务器
 int main() {
     WSADATA wsa_data; //WSADATA变量,包含windows socket执行的信息
     int i_result = ; //接收返回值
     SOCKET sock_server = INVALID_SOCKET; //创建服务器套接字
     SOCKET sock_client = INVALID_SOCKET; //创建客户端套接字
     //addrinfo是getaddrinfo()函数用来保存主机地址信息的结构体
     addrinfo *result = nullptr; //result是存储地址信息的链表
     addrinfo hints;
     //初始化winsock动态库(ws2_32.dll),MAKEWORD(2, 2)用于请求使用winsock2.2版本
     i_result = WSAStartup(MAKEWORD(, ), &wsa_data);
     if (i_result != ) {
         cerr << "WSAStartup() function failed: " << i_result << "\n";
         system("pause");
         return ;
     }
     //用0填充内存区域,是ZeroMemory的更安全版本
     SecureZeroMemory(&hints, sizeof(addrinfo));
     hints.ai_family = AF_INET;
     hints.ai_socktype = SOCK_STREAM; //流式套接字用于TCP协议
     hints.ai_protocol = IPPROTO_TCP;
     hints.ai_flags = AI_PASSIVE; //socket的地址会被用于bind()函数的调用
     //确定服务器的地址与端口,将相关信息写入result中
     i_result = getaddrinfo(nullptr, DEFAULT_PORT, &hints, &result);
     if (i_result != ) {
         cerr << "getaddrinfo() function failed with error: " << WSAGetLastError() << "\n";
         WSACleanup();
         system("pause");
         return ;
     }
     //创建服务器套接字
     sock_server = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
     //套接字创建失败
     if (sock_server == INVALID_SOCKET) {
         cerr << "socket() function failed with error: " << WSAGetLastError() << "\n";
         //将getaddrinfo()函数动态分配的addrinfo中的地址信息释放掉
         freeaddrinfo(result);
         //释放套接字资源
         WSACleanup();
         system("pause");
         return ;
     }
     //将服务器套接字与地址对象绑定,result->ai_addr是结构体的指针
     i_result = bind(sock_server, result->ai_addr, static_cast<int>(result->ai_addrlen));
     //绑定失败
     if (i_result == SOCKET_ERROR) {
         cerr << "bind() function failed with error: " << WSAGetLastError() << "\n";
         freeaddrinfo(result);
         closesocket(sock_server);
         WSACleanup();
         system("pause");
         return ;
     }
     freeaddrinfo(result);
     cout << "server started successfully..." << endl;
     //开始监听
     cout << "start listening..." << endl;
     i_result = listen(sock_server, SOMAXCONN);
     if (i_result == SOCKET_ERROR) {
         cerr << "listen() function failed with error: " << WSAGetLastError() << "\n";
         closesocket(sock_server);
         system("pause");
         return ;
     }
     //接收客户端请求,获取客户端ip地址
     SOCKADDR_IN addr_client;
     int len_addr = sizeof(SOCKADDR_IN);
     char ip_buf[IP_BUF_SIZE];
     SecureZeroMemory(ip_buf, IP_BUF_SIZE);
     sock_client = accept(sock_server, (SOCKADDR*)&addr_client, &len_addr);
     if (sock_client == INVALID_SOCKET) {
         cerr << "accept() function failed with error: " << WSAGetLastError() << "\n";
         closesocket(sock_server);
         WSACleanup();
         system("pause");
         return ;
     }
     cout << "client connected..." << endl;
     //ip地址转换
     inet_ntop(AF_INET, &addr_client, ip_buf, IP_BUF_SIZE);
     cout << "client ip address: " << ip_buf << endl;
     //接收和发送数据
     char recv_buf[RECV_BUF_SIZE];
     int send_result = ;
     do {
         //不可缺少,若不将内存空间清零会输出乱码,这是因为输送过来的信息未必有256个字节
         SecureZeroMemory(recv_buf, RECV_BUF_SIZE);
         //标志位一般设置为0
         i_result = recv(sock_client, recv_buf, RECV_BUF_SIZE, );
         if (i_result > ) {
             //exit表示客户端请求断开连接
             if (strcmp(recv_buf, "exit") == ) {
                 cout << "client requests to close the connection..." << endl;
                 break;
             }
             //输出接收的字节数
             cout << "Bytes received: " << i_result << endl;
             cout << "message received: " << recv_buf << endl;
             //向客户端发送接收到的数据
             send_result = send(sock_client, recv_buf, i_result, );
             if (send_result == SOCKET_ERROR) {
                 cerr << "send() function failed with error: " << WSAGetLastError() << "\n";
                 closesocket(sock_client);
                 WSACleanup();
                 system("pause");
                 return ;
             }
         }
         //i_result的值为0表示连接已经关闭
         else if (i_result == ) {
             cout << "connection closed..." << endl;
         }
         else {
             cerr << "recv() function failed with error: " << WSAGetLastError() << "\n";
             closesocket(sock_client);
             WSACleanup();
             system("pause");
             return ;
         }
     } while (i_result > ); //do...while语句后注意要有分号
     //shutdown()禁用套接字的接收或发送功能
     i_result = shutdown(sock_client, SD_SEND);
     if (i_result == SOCKET_ERROR) {
         cerr << "shutdown() function failed with error: " << WSAGetLastError() << "\n";
         closesocket(sock_client);
         WSACleanup();
         system("pause");
         return ;
     }
     //关闭套接字
     i_result = closesocket(sock_server);
     WSACleanup();
     cout << "socket closed..." << endl;
     system("pause");
     return ;
 }

客户端：

 #include <iostream>
 #include <WinSock2.h>
 #include <Ws2tcpip.h>

 #pragma comment(lib, "ws2_32.lib")

 using std::cin;
 using std::cerr;
 using std::cout;
 using std::endl;
 using std::flush;

 const char DEFAULT_PORT[] = "";
 const int SEND_BUF_SIZE = ;

 //客户端
 int main() {
     WSADATA wsa_data; //WSADATA变量,包含windows socket执行的信息
     int i_result = ; //接收返回值
     SOCKET sock_client = INVALID_SOCKET;
     addrinfo *result = nullptr, hints;
     //初始化winsock动态库(ws2_32.dll),MAKEWORD(2, 2)用于请求使用winsock2.2版本
     i_result = WSAStartup(MAKEWORD(, ), &wsa_data);
     if (i_result != ) {
         cerr << "WSAStartup() function failed: " << i_result << "\n";
         system("pause");
         return ;
     }
     SecureZeroMemory(&hints, sizeof(hints));
     hints.ai_family = AF_UNSPEC;
     hints.ai_socktype = SOCK_STREAM;
     hints.ai_protocol = IPPROTO_TCP;
     //
     i_result = getaddrinfo("127.0.0.1", DEFAULT_PORT, &hints, &result);
     if (i_result != ) {
         cerr << "getaddrinfo() function failed with error: " << WSAGetLastError() << "\n";
         WSACleanup();
         system("pause");
         return ;
     }
     //创建套接字
     sock_client = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
     if (sock_client == INVALID_SOCKET) {
         cerr << "socket() function failed with error: " << WSAGetLastError() << "\n";
         WSACleanup();
         system("pause");
         return ;
     }
     //连接服务器
     i_result = connect(sock_client, result->ai_addr, result->ai_addrlen);
     if (i_result == SOCKET_ERROR) {
         cerr << "connect() function failed with error: " << WSAGetLastError() << "\n";
         WSACleanup();
         system("pause");
         return ;
     }
     cout << "connect server successfully..." << endl;
     //
     freeaddrinfo(result);
     //
     char send_buf[SEND_BUF_SIZE];
     int recv_result = ;
     //SecureZeroMemory(send_buf, SEND_BUF_SIZE);
     do {
         cout << "enter the message that you want to send: " << flush;
         cin.getline(send_buf, SEND_BUF_SIZE);
         i_result = send(sock_client, send_buf, static_cast<int>(strlen(send_buf)), );
         if (i_result == SOCKET_ERROR) {
             cerr << "send() function failed with error: " << WSAGetLastError() << "\n";
             closesocket(sock_client);
             WSACleanup();
             system("pause");
             return ;
         }
         cout << "Bytes sent: " << i_result << endl;
         //接收服务器返回的数据
         recv_result = recv(sock_client, send_buf, SEND_BUF_SIZE, );
         if (recv_result > ) {
             cout << "feedback from server: " << send_buf << endl;
         }
         else if (recv_result == ) {
             cout << "connection closed..." << endl;
         }
         else {
             cerr << "recv() function failed with error: " << WSAGetLastError() << "\n";
             closesocket(sock_client);
             WSACleanup();
             system("pause");
             return ;
         }
     } while (recv_result > );
     //
     i_result = shutdown(sock_client, SD_SEND);
     if (i_result == SOCKET_ERROR) {
         cerr << "shutdown() function failed with error: " << WSAGetLastError() << "\n";
         closesocket(sock_client);
         WSACleanup();
         system("pause");
         return ;
     }
     closesocket(sock_client);
     WSACleanup();
     cout << "socket closed..." << endl;
     system("pause");
     return ;
 }