基于UDP的IO多路复用一例

服务器端：

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

typedef struct sockaddr SA;
#define N 256

int main(int argc, char *argv[])
{
    int sockfd;
    char buffer[N];
    char buffer2[N];
    struct sockaddr_in myaddr, peeraddr;
    socklen_t peerlen = sizeof(peeraddr);
    int maxfd;
    int i;

    fd_set rdfs;

    if((sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("fail to socket");
        exit(-1);
    }

    bzero(&myaddr, sizeof(myaddr));
    myaddr.sin_family = PF_INET;
    myaddr.sin_port = htons(atoi(argv[2]));
    myaddr.sin_addr.s_addr = inet_addr(argv[1]);

    if(bind(sockfd, (SA *)&myaddr, sizeof(myaddr)) < 0)
    {
        perror("fail to bind");
        exit(-1);
    }

    bzero(&peeraddr, peerlen);
    maxfd = sockfd;


    while(1)
    {
        FD_ZERO(&rdfs);
        FD_SET(0, &rdfs);
        FD_SET(sockfd, &rdfs);

        select(maxfd+1, &rdfs, NULL, NULL, NULL);

        for(i=0; i<=maxfd; i++)
        {
            if(FD_ISSET(i, &rdfs) == 1)
            {
                if(i == 0)
                {
                    fgets(buffer2, N, stdin);
                    printf("you input %s", buffer2);
                }
                if(i == sockfd)
                {
                    recvfrom(sockfd, buffer, N, 0, (SA *)&peeraddr, &peerlen);
                    sendto(sockfd, buffer, N, 0, (SA *)&peeraddr, peerlen);
                }
            }
        }

    }

    return 0;
}

客户端：

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

typedef struct sockaddr SA;
#define N 256

int main(int argc, char *argv[])
{
    int sockfd;
    char buffer[N];
    struct sockaddr_in serveraddr;

    if((sockfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("fail to socket");
        exit(-1);
    }

    bzero(&serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = PF_INET;
    serveraddr.sin_port = htons(atoi(argv[2]));
    serveraddr.sin_addr.s_addr = inet_addr(argv[1]);

    while(1)
    {
        fgets(buffer, N, stdin);
        if(strncmp(buffer, "quit", 4) == 0)
        {
            break;
        }
        sendto(sockfd, buffer, N, 0, (SA *)&serveraddr, sizeof(serveraddr));
        bzero(buffer, N);
        recvfrom(sockfd, buffer, N, 0, NULL, NULL);
        printf("receive from server > %s",buffer);
    }
    close(sockfd);
    return 0;
}

运行：