UDP服务端

#ifdef _WIN32                           
#define _WINSOCK_DEPRECATED_NO_WARNINGS  #define close closesocket              
#include <winsock2.h>
#else  
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#endif#include <stdio.h>
#include <stdlib.h>
#include <string.h>#define PORT 8080  
#define MAXLINE 1024#ifdef _WIN32
void cleanup() { WSACleanup(); }
#endifint main()
{
#ifdef _WIN32WSADATA wsData;if (WSAStartup(MAKEWORD(2, 2), &wsData) != 0){perror("WSA Startup error: \n");return 0;}atexit(cleanup); 
#endifint sockfd;char buffer[MAXLINE];char *hello = "Hello from server";struct sockaddr_in servaddr, cliaddr;/* 创建socket */if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0){perror("socket creation failed");exit(EXIT_FAILURE);}memset(&servaddr, 0, sizeof(servaddr));memset(&cliaddr, 0, sizeof(cliaddr));servaddr.sin_family = AF_INET;  // IPv4servaddr.sin_addr.s_addr = INADDR_ANY;servaddr.sin_port = htons(PORT);/* 绑定服务端地址 */if (bind(sockfd, (const struct sockaddr *)&servaddr, sizeof(servaddr)) < 0){perror("bind failed");exit(EXIT_FAILURE);}unsigned int len;int n;n = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL,(struct sockaddr *)&cliaddr, &len);buffer[n] = '\0';printf("Client : %s\n", buffer);sendto(sockfd, (const char *)hello, strlen(hello), 0,(const struct sockaddr *)&cliaddr, len);printf("Hello message sent.\n");close(sockfd);return 0;
}

UDP客户端

#ifdef _WIN32                           
#define _WINSOCK_DEPRECATED_NO_WARNINGS  #include <winsock2.h>
#define close closesocket 
#else                  
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
#endif#include <stdio.h>
#include <stdlib.h>
#include <string.h>#define PORT 8080 
#define MAXLINE 1024#ifdef _WIN32
void cleanup() { WSACleanup(); }
#endifint main()
{
#ifdef _WIN32WSADATA wsData;if (WSAStartup(MAKEWORD(2, 2), &wsData) != 0){perror("WSA Startup error: \n");return 0;}atexit(cleanup); 
#endifint sockfd;char buffer[MAXLINE];char *hello = "Hello from client";struct sockaddr_in servaddr;/* 创建用户数据报类型的socket */if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0){perror("socket creation failed");exit(EXIT_FAILURE);}memset(&servaddr, 0, sizeof(servaddr));/* 填充协议信息 */servaddr.sin_family = AF_INET;servaddr.sin_port = htons(PORT);servaddr.sin_addr.s_addr = INADDR_ANY;int n;unsigned int len;sendto(sockfd, (const char *)hello, strlen(hello), 0,(const struct sockaddr *)&servaddr, sizeof(servaddr));printf("Hello message sent.\n");n = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL,(struct sockaddr *)&servaddr, &len);buffer[n] = '\0';printf("Server : %s\n", buffer);close(sockfd);return 0;
}

客户端运行结果：

Hello message sent.
Server : Hello from server
 

服务端运行结果：

Client : Hello from client
Hello message sent.