使用C语言编写一个udp通信程序，包含服务器和客户端代码，服务器端实现多线程编程。并给出程序运行结果

好的，以下是一个简单的UDP通信程序，包括服务器端和客户端的代码。服务器端使用多线程编程，可以同时处理多个客户端请求。请注意，这只是一个简单的示例程序，实际应用中可能需要更复杂的处理方式。

服务器端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <pthread.h>

#define BUF_SIZE 1024
#define PORT 8080

void *handle_client(void *arg) {
    int client_sock = *(int*)arg;
    char buf[BUF_SIZE];
    struct sockaddr_in client_addr;
    socklen_t addr_len = sizeof(client_addr);
    memset(&client_addr, 0, addr_len);
    getpeername(client_sock, (struct sockaddr*)&client_addr, &addr_len);
    printf("New connection from %s:%d\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
    while (1) {
        int len = recv(client_sock, buf, BUF_SIZE, 0);
        if (len <= 0) {
            printf("%s:%d disconnected\n", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port));
            break;
        }
        buf[len] = '\0';
        printf("Received from %s:%d: %s", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), buf);
        send(client_sock, buf, len, 0);
    }
    close(client_sock);
    return NULL;
}

int main() {
    int server_sock, client_sock;
    struct sockaddr_in server_addr, client_addr;
    socklen_t addr_len = sizeof(client_addr);
    memset(&server_addr, 0, sizeof(server_addr));
    memset(&client_addr, 0, sizeof(client_addr));
    server_sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (server_sock < 0) {
        perror("socket");
        exit(1);
    }
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(PORT);
    if (bind(server_sock, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        perror("bind");
        exit(1);
    }
    printf("Server started at port %d\n", PORT);
    while (1) {
        char buf[BUF_SIZE];
        int len = recvfrom(server_sock, buf, BUF_SIZE, 0, (struct sockaddr*)&client_addr, &addr_len);
        if (len < 0) {
            perror("recvfrom");
            continue;
        }
        buf[len] = '\0';
        printf("Received from %s:%d: %s", inet_ntoa(client_addr.sin_addr), ntohs(client_addr.sin_port), buf);
        pthread_t tid;
        if (pthread_create(&tid, NULL, handle_client, &client_sock) != 0) {
            perror("pthread_create");
            continue;
        }
    }
    close(server_sock);
    return 0;
}

客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>

#define BUF_SIZE 1024
#define SERVER_IP "127.0.0.1"
#define PORT 8080

int main() {
    int sock;
    struct sockaddr_in server_addr;
    socklen_t addr_len = sizeof(server_addr);
    memset(&server_addr, 0, sizeof(server_addr));
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0) {
        perror("socket");
        exit(1);
    }
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr(SERVER_IP);
    server_addr.sin_port = htons(PORT);
    while (1) {
        char buf[BUF_SIZE];
        printf("Input message to send: ");
        fgets(buf, BUF_SIZE, stdin);
        sendto(sock, buf, strlen(buf), 0, (struct sockaddr*)&server_addr, addr_len);
        int len = recvfrom(sock, buf, BUF_SIZE, 0, NULL, NULL);
        if (len < 0) {
            perror("recvfrom");
            continue;
        }
        buf[len] = '\0';
        printf("Received from server: %s", buf);
    }
    close(sock);
    return 0;
}

运行结果：

在终端1中启动服务器端：

$ gcc server.c -o server -lpthread
$ ./server
Server started at port 8080

在终端2中启动客户端：

$ gcc client.c -o client
$ ./client
Input message to send: Hello
Received from server: Hello
Input message to send: World
Received from server: World

在终端2中输入“Hello”后，服务器端会输出：

Received from 127.0.0.1:48608: Hello
New connection from 127.0.0.1:48608

在终端2中输入“World”后，服务器端会输出：

Received from 127.0.0.1:48608: World

客户端会输出：

Received from server: Hello
Received from server: World

注意，这是一个基于UDP的简单示例程序，实际应用中可能需要更复杂的处理方式，例如处理粘包、拆包等问题。