使用SO_RCVTIMEO套接字选项为recvfrom设置超时

#include"apue.h"
void do_cli(FILE* fp,int sockfd,const (SA*)pserveraddr,socklen_t len)
{
    char sendbuf[maxlen],recvbuf[maxlen];
    int n;
    struct timeval tv;
    tv.tv_sec=5;tv.tv_usec=0;
    setsockopt(sockfd,SOL_SOCKET,SO_RCVTIMEO,&tv,sizeof(tv));    //set 5 sec time out 
    while((fgets(sendbuf,maxlen,fp))!=NULL)
    {
        sendto(sockfd,sendbuf,strlen(sendbuf),0,pserveraddr,len);
        n=recvfrom(sockfd,recvbuf,maxlen,0,NULL,NULL);
        if(n<0)
        {
            if(errno==EWOULDBLOCK)        //time over but still have not recv from server.
            {
                fprintf(stderr,"time out!
");
                continue;
            }
            else    //other error reason
            {
                perror("read error!
");
                continue;
            }
        }
        else
        {
            recvbuf[n]='';
            fputs(recvbuf,stdout);
        }
        
    }
} 

使用了 setsockopt函数，本例仅使用了读操作超时，若是想使用写操作超时使用SO_SNDTIMEO选项。读操作超时使用SO_RCVTIMEO.