c++ udp 服务端 多线程代码

很好，我可以为您提供C语言编写的UDP服务端多线程代码示例：

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

#define MAXLINE 1024
#define SERV_PORT 8888

struct s_info {
    struct sockaddr_in cliaddr;
    int connfd;
};

void* do_work(void* arg);

int main(int argc, char** argv) {
    int listenfd, connfd;
    pthread_t tid;
    struct sockaddr_in servaddr, cliaddr;
    socklen_t len = sizeof(cliaddr);
    char buf[MAXLINE];
    listenfd = socket(AF_INET, SOCK_DGRAM, 0);
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);
    bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr));
    printf("Accepting connections ...\n");
    while (1) {
        memset(buf, 0, sizeof(buf));
        int n = recvfrom(listenfd, buf, MAXLINE, 0, (struct sockaddr*)&cliaddr, &len);
        printf("Received from %s at PORT %d\n",
               inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port));
        struct s_info* ts = (struct s_info*)malloc(sizeof(struct s_info));
        ts->cliaddr = cliaddr;
        ts->connfd = listenfd;
        pthread_create(&tid, NULL, do_work, (void*)ts);
    }
    return 0;
}

void* do_work(void* arg) {
    pthread_t tid = pthread_self();
    struct s_info* ts = (struct s_info*)arg;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];
    memset(buf, 0, sizeof(buf));
    inet_ntop(AF_INET, &(*ts).cliaddr.sin_addr, str, sizeof(str));
    printf("Thread with ID %ld servicing %s:%d\n", tid, str, ntohs((*ts).cliaddr.sin_port));
    while (1) {
        int n = recvfrom((*ts).connfd, buf, MAXLINE, 0, (struct sockaddr*)&(*ts).cliaddr, &len);
        if (n == 0) {
            printf("The client %s:%d has closed the connection\n", str, ntohs((*ts).cliaddr.sin_port));
            break;
        }
        printf("Received from %s at PORT %d: %s\n",
               inet_ntoa((*ts).cliaddr.sin_addr), ntohs((*ts).cliaddr.sin_port), buf);
        sendto((*ts).connfd, buf, n, 0, (struct sockaddr*)&(*ts).cliaddr, len);
    }
    close((*ts).connfd);
    free(ts);
    pthread_exit(NULL);
}

此代码实现了一个简单的UDP服务端，它能够接收来自任意IP地址和端口号的UDP数据报文，并把接收到的数据原封不动地发回给客户端。此服务端是一个基于多线程的实现，可以同时服务多个客户端。每个客户端都分配一个线程来处理其请求。