Visual Studio 2022 中可以运行的 UDP 客户端和服务器的示例代码。这个示例使用 C++ 和 Windows Socket API 来实现 UDP 通信。

服务器端代码（udp_server.cpp）

#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>#pragma comment(lib, "Ws2_32.lib")#define DEFAULT_PORT "27015"
#define DEFAULT_BUFLEN 512int main() {WSADATA wsaData;int iResult;// 初始化 WinsockiResult = WSAStartup(MAKEWORD(2, 2), &wsaData);if (iResult != 0) {std::cout << "WSAStartup failed: " << iResult << std::endl;return 1;}struct addrinfo *result = NULL, *ptr = NULL, hints;ZeroMemory(&hints, sizeof(hints));hints.ai_family = AF_INET;hints.ai_socktype = SOCK_DGRAM;hints.ai_protocol = IPPROTO_UDP;hints.ai_flags = AI_PASSIVE;// 解析本地地址和端口iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);if (iResult != 0) {std::cout << "getaddrinfo failed: " << iResult << std::endl;WSACleanup();return 1;}SOCKET ListenSocket = INVALID_SOCKET;// 创建监听套接字ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);if (ListenSocket == INVALID_SOCKET) {std::cout << "socket failed: " << WSAGetLastError() << std::endl;freeaddrinfo(result);WSACleanup();return 1;}// 绑定套接字iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);if (iResult == SOCKET_ERROR) {std::cout << "bind failed: " << WSAGetLastError() << std::endl;freeaddrinfo(result);closesocket(ListenSocket);WSACleanup();return 1;}freeaddrinfo(result);char recvbuf[DEFAULT_BUFLEN];int recvbuflen = DEFAULT_BUFLEN;struct sockaddr_in clientAddr;int clientAddrLen = sizeof(clientAddr);std::cout << "UDP Server is listening on port " << DEFAULT_PORT << std::endl;while (true) {// 接收数据iResult = recvfrom(ListenSocket, recvbuf, recvbuflen, 0, (struct sockaddr*)&clientAddr, &clientAddrLen);if (iResult > 0) {recvbuf[iResult] = '\0';std::cout << "Received from client: " << recvbuf << std::endl;// 回显数据给客户端iResult = sendto(ListenSocket, recvbuf, iResult, 0, (struct sockaddr*)&clientAddr, clientAddrLen);if (iResult == SOCKET_ERROR) {std::cout << "sendto failed: " << WSAGetLastError() << std::endl;}}else if (iResult == 0) {std::cout << "Connection closing..." << std::endl;}else {std::cout << "recvfrom failed: " << WSAGetLastError() << std::endl;}}// 关闭套接字closesocket(ListenSocket);WSACleanup();return 0;
}

客户端代码（udp_client.cpp）

#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>#pragma comment(lib, "Ws2_32.lib")#define DEFAULT_PORT "27015"
#define DEFAULT_BUFLEN 512
#define DEFAULT_SERVER_IP "127.0.0.1"int main() {WSADATA wsaData;int iResult;// 初始化 WinsockiResult = WSAStartup(MAKEWORD(2, 2), &wsaData);if (iResult != 0) {std::cout << "WSAStartup failed: " << iResult << std::endl;return 1;}struct addrinfo *result = NULL, *ptr = NULL, hints;ZeroMemory(&hints, sizeof(hints));hints.ai_family = AF_INET;hints.ai_socktype = SOCK_DGRAM;hints.ai_protocol = IPPROTO_UDP;// 解析服务器地址和端口iResult = getaddrinfo(DEFAULT_SERVER_IP, DEFAULT_PORT, &hints, &result);if (iResult != 0) {std::cout << "getaddrinfo failed: " << iResult << std::endl;WSACleanup();return 1;}SOCKET ConnectSocket = INVALID_SOCKET;// 创建套接字ConnectSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);if (ConnectSocket == INVALID_SOCKET) {std::cout << "socket failed: " << WSAGetLastError() << std::endl;freeaddrinfo(result);WSACleanup();return 1;}char sendbuf[DEFAULT_BUFLEN];char recvbuf[DEFAULT_BUFLEN];int recvbuflen = DEFAULT_BUFLEN;std::cout << "Enter a message to send to the server: ";std::cin.getline(sendbuf, DEFAULT_BUFLEN);// 发送数据到服务器iResult = sendto(ConnectSocket, sendbuf, (int)strlen(sendbuf), 0, result->ai_addr, (int)result->ai_addrlen);if (iResult == SOCKET_ERROR) {std::cout << "sendto failed: " << WSAGetLastError() << std::endl;freeaddrinfo(result);closesocket(ConnectSocket);WSACleanup();return 1;}struct sockaddr_in serverAddr;int serverAddrLen = sizeof(serverAddr);// 接收服务器的响应iResult = recvfrom(ConnectSocket, recvbuf, recvbuflen, 0, (struct sockaddr*)&serverAddr, &serverAddrLen);if (iResult > 0) {recvbuf[iResult] = '\0';std::cout << "Received from server: " << recvbuf << std::endl;}else if (iResult == 0) {std::cout << "Connection closed by server." << std::endl;}else {std::cout << "recvfrom failed: " << WSAGetLastError() << std::endl;}// 清理资源freeaddrinfo(result);closesocket(ConnectSocket);WSACleanup();return 0;
}

代码解释

• 服务器端：

  1. 初始化 Winsock：调用 WSAStartup 函数初始化 Windows Sockets DLL。
  2. 解析地址和端口：使用 getaddrinfo 函数解析本地地址和端口。
  3. 创建和绑定套接字：使用 socket 函数创建 UDP 套接字，并使用 bind 函数将套接字绑定到指定的地址和端口。
  4. 接收和发送数据：使用 recvfrom 函数接收客户端发送的数据，并使用 sendto 函数将数据回显给客户端。

• 客户端：

  1. 初始化 Winsock：同样调用 WSAStartup 函数初始化 Windows Sockets DLL。
  2. 解析服务器地址和端口：使用 getaddrinfo 函数解析服务器的地址和端口。
  3. 创建套接字：使用 socket 函数创建 UDP 套接字。
  4. 发送和接收数据：使用 sendto 函数向服务器发送数据，并使用 recvfrom 函数接收服务器的响应。

在 VS2022 中运行步骤

1. 打开 Visual Studio 2022，创建一个新的控制台应用程序项目。
2. 将上述服务器端代码复制到一个 .cpp 文件中，例如 udp_server.cpp；将客户端代码复制到另一个 .cpp 文件中，例如 udp_client.cpp。
3. 分别编译和运行这两个程序。先运行服务器端程序，然后运行客户端程序，在客户端输入要发送的消息，客户端将消息发送给服务器，服务器接收到消息后将其回显给客户端。