基于UDP套接字编程实例

data.h

#ifndef DATA_H
#define DATA_H
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <stdlib.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#define PORT 4578
#define maxn 100

#endif

server.c

#include "data.h"
int main()
{
    int sockfd;
    struct sockaddr_in server;
    struct sockaddr_in client;
    socklen_t len;
    int num;
    char buf[maxn];
    if((sockfd = socket(AF_INET,SOCK_DGRAM,0)) == -1)
    {
        fprintf(stderr,"socket fail,error:%s
",strerror(errno));
        return -1;
    }
    bzero(&server,sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(PORT);
    server.sin_addr.s_addr = htonl(INADDR_ANY);
    if(bind(sockfd,(struct sockaddr*)&server,sizeof(server)) == -1)
    {
        fprintf(stderr,"bind fail,error:%s
",strerror(errno));
        return -1;
    }
    len = sizeof(client);
    bzero(&buf,sizeof(buf));
    while(1)
    {
        num = recvfrom(sockfd,buf,maxn,0,(struct sockaddr*)&client,&len);
        if(num < 0)
        {
            perror("recvfrom() error!
");
            exit(1);
        }
        num--;
        buf[num] = '';
        printf("You got a message <%s> from client.
",buf);
        printf("It is ip is %s,port is %d.
",
            inet_ntoa(client.sin_addr), htons(client.sin_port));
        sendto(sockfd,buf,strlen(buf),0,(struct sockaddr*)&client,len);
        if(!strcmp(buf,"bye"))
            break;
    }
    close(sockfd);

}

client.c

#include "data.h"
int main()
{
    int sockfd,num;
    char sendbuf[maxn];
    char recvbuf[maxn];
    struct sockaddr_in server;
    struct sockaddr_in peer;
    if((sockfd = socket(AF_INET,SOCK_DGRAM,0)) == -1)
    {
        fprintf(stderr,"socket fail,error %s
",strerror(errno));
        exit(1);
    }
    bzero(&server,sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(PORT);    
    server.sin_addr.s_addr = inet_addr("127.0.0.1");
    bzero(&sendbuf,sizeof(sendbuf));
    bzero(&recvbuf,sizeof(recvbuf));
    while(fgets(sendbuf,sizeof(sendbuf),stdin) != NULL)
    {
        int tt = strlen(sendbuf);
        sendto(sockfd,sendbuf,tt,0,(struct sockaddr*)&server,sizeof(server));
        socklen_t len;
        recvfrom(sockfd,recvbuf,maxn,0,NULL,NULL);
        printf("receive message is :");
        fputs(recvbuf,stdout);
        printf("
");
        bzero(&sendbuf,sizeof(sendbuf));
        bzero(&recvbuf,sizeof(recvbuf));
    }
    close(sockfd);
    return 0;
}

运行结果：