Linux--Socket 编程 UDP（简单的回显服务器和客户端代码）

以下是一个简单的UDP回显服务器和客户端的示例代码。服务器监听在端口9999上，并将接收到的任何消息发送回客户端。客户端连接到服务器并发送消息，然后接收回显。

服务器端 (server.c):

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
 
#define BUF_SIZE 1024
#define PORT 9999
 
int main() {
    int server_fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (server_fd < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }
 
    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
 
    int bind_ret = bind(server_fd, (struct sockaddr *)&server_addr, sizeof(server_addr));
    if (bind_ret < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }
 
    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    char buffer[BUF_SIZE];
    int read_len;
 
    while (1) {
        memset(buffer, 0, BUF_SIZE);
        read_len = recvfrom(server_fd, buffer, BUF_SIZE, 0, (struct sockaddr *)&client_addr, &client_addr_len);
        if (read_len < 0) {
            perror("recvfrom failed");
            exit(EXIT_FAILURE);
        }
        printf("Received message: %s\n", buffer);
 
        int send_ret = sendto(server_fd, buffer, read_len, 0, (struct sockaddr *)&client_addr, client_addr_len);
        if (send_ret < 0) {
            perror("sendto failed");
            exit(EXIT_FAILURE);
        }
    }
 
    close(server_fd);
    return 0;
}

客户端 (client.c):

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
 
#define BUF_SIZE 1024
#define PORT 9999
#define SERVER_IP "127.0.0.1"
 
int main() {
    int client_fd = socket(AF_INET, SOCK_DGRAM, 0);
    if (client_fd < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }
 
    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(PORT);
    inet_pton(AF_INET, SERVER_IP, &server_addr.sin_addr);
 
    char buffer[BUF_SIZE];
    printf("Enter message: ");
    fgets(buffer, BUF_SIZE, stdin);
 
    int send_ret = sendto(client_fd, buffer, strlen(buffer),