UDP超时处理

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


#define MAXLINE 80
#define SERV_PORT 2514

int
main( char * agrv[], int argc)
... {
    int sockfd;
    struct sockaddr_in servaddr, cliaddr;

    sockfd = socket(AF_INET, SOCK_DGRAM, 0); /**//* create a socket */

    /**//* init servaddr */
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);

    /**//* bind address and port to socket */
    if(bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) == -1)
    ...{
        perror("bind error");
        exit(1);
    }

    fd_set rfds;
    struct timeval tv;
    int retval;

    /**//* Watch stdin (fd 0) to see when it has input. */

    FD_ZERO(&rfds);
    FD_SET(sockfd, &rfds);

    /**//* Wait up to five seconds. */
    tv.tv_sec = 5;
    tv.tv_usec = 0;

    retval = select(sockfd + 1, &rfds, NULL, NULL, &tv);
    /**//* Don't rely on the value of tv now! */

    socklen_t len;
    char mesg[1024];
    struct sockaddr *pcliaddr;

    if (retval == -1)
        perror("select()");
    else if (retval)
    ...{
        printf("Data is available now. ");
        recvfrom(sockfd, mesg, 1024, 0, pcliaddr, &len);
        printf("%s ", mesg);
    }
    else
        printf("No data within five seconds. ");

    close(sockfd);

    return 0;
}