请用C++winsock2写一个TCP/IP文件传输（指定ip和端口）的客户端和服务器的完整实例

C++的Winsock2库主要用于Windows平台下的网络编程，包括TCP/IP协议。以下是一个简单的TCP/IP文件传输的客户端和服务器的例子，假设我们只处理文本文件的上传和下载： **服务器端（server.cpp）：** ```cpp #include <winsock2.h> #include <ws2tcpip.h> #include <iostream> #include <fstream> #pragma comment(lib, "Ws2_32.lib") const char* serverIP = "127.0.0.1"; int serverPort = 9000; // 创建套接字、绑定地址、监听等 SOCKET serverSocket; void initServer() { WSADATA wsaData; if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) { std::cerr << "Error initializing Winsock." << std::endl; return; } serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (serverSocket == INVALID_SOCKET) { std::cerr << "Error creating socket." << std::endl; WSACleanup(); return; } sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_addr.s_addr = inet_addr(serverIP); serverAddr.sin_port = htons(serverPort); if (bind(serverSocket, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) { std::cerr << "Error binding to address." << std::endl; closesocket(serverSocket); WSACleanup(); return; } listen(serverSocket, SOMAXCONN); // 监听连接 std::cout << "Server listening on " << serverIP << ":" << serverPort << std::endl; } // 处理客户端请求 void handleClient(SOCKET clientSocket) { char buffer[1024]; int bytesRead; while ((bytesRead = recv(clientSocket, buffer, sizeof(buffer), 0)) > 0) { std::string message(buffer, bytesRead); if (message == "upload") { // 接收上传指令 std::ifstream file("file.txt", std::ios::binary); if (file.is_open()) { send(clientSocket, "Upload started.", strlen("Upload started."), 0); std::copy(file.rdbuf(), file.rdbuf() + file.gcount(), buffer); send(clientSocket, buffer, file.gcount(), 0); file.close(); } else { send(clientSocket, "File not found.", strlen("File not found."), 0); } } else if (message == "download") { // 接收下载指令 send(clientSocket, "Downloading...", strlen("Downloading..."), 0); std::ofstream outputFile("file.txt", std::ios::binary | std::ios::out); if (!outputFile) { send(clientSocket, "Failed to create output file.", strlen("Failed to create output file."), 0); } else { sendfile(clientSocket, stdout, NULL, -1, NULL, NULL); outputFile.close(); send(clientSocket, "Download completed.", strlen("Download completed."), 0); } } else { send(clientSocket, "Unknown command.", strlen("Unknown command."), 0); } } if (bytesRead == 0 || bytesRead == -1) { // 错误或关闭 shutdown(clientSocket, SD_SEND); closesocket(clientSocket); } } int main() { initServer(); while (true) { SOCKET clientSocket = accept(serverSocket, NULL, NULL); if (clientSocket == INVALID_SOCKET) { break; // 处理错误 } std::cout << "Accepted connection from " << inet_ntoa(((sockaddr_in*)getpeername(clientSocket))->sin_addr) << "." << std::endl; handleClient(clientSocket); } closesocket(serverSocket); WSACleanup(); return 0; } ``` **客户端（client.cpp）：** ```cpp #include <winsock2.h> #include <ws2tcpip.h> #include <iostream> const char* serverIP = "127.0.0.1"; int serverPort = 9000; void connectToServer() { WSADATA wsaData; if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) { std::cerr << "Error initializing Winsock." << std::endl; return; } SOCKET clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (clientSocket == INVALID_SOCKET) { std::cerr << "Error creating socket." << std::endl; WSACleanup(); return; } sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_addr.s_addr = inet_addr(serverIP); serverAddr.sin_port = htons(serverPort); if (connect(clientSocket, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR) { std::cerr << "Error connecting to server." << std::endl; closesocket(clientSocket); WSACleanup(); return; } std::string command; std::getline(std::cin, command); switch (command[0]) { case 'u': // 上传 std::ifstream file("file.txt", std::ios::binary); if (file.is_open()) { send(clientSocket, "Uploading...", strlen("Uploading..."), 0); std::copy(file.rdbuf(), file.rdbuf() + file.gcount(), buffer); send(clientSocket, buffer, file.gcount(), 0); file.close(); std::cout << "Uploaded successfully.\n"; } else { std::cerr << "File not found.\n"; } break; case 'd': // 下载 std::ofstream outputFile("file.txt", std::ios::binary | std::ios::out); if (!outputFile) { std::cerr << "Failed to create output file.\n"; } else { send(clientSocket, "Downloading...\n", strlen("Downloading...\n"), 0); sendfile(clientSocket, outputFile.getHandle(), NULL, -1, NULL, NULL); outputFile.close(); std::cout << "Downloaded successfully.\n"; } break; default: std::cerr << "Invalid command.\n"; break; } closesocket(clientSocket); WSACleanup(); } int main() { connectToServer(); return 0; } ``` 注意：这是一个简化的示例，实际应用需要处理更多的边界情况，并添加异常处理和错误消息。同时，`sendfile`函数用于高效的文件传输。