select();函数：
select函数原型：
int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeval);
void FD_CLR(int fd, fd_set *set);
int FD_ISSET(int fd, fd_set *set);
void FD_SET(int fd, fd_set *set);
void FD_ZERO(fd_set *set);
服务器程序：
#define SIZE 32
int main()
{
int sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd==-1)
{
perror("socket");
return -1;
}
struct sockaddr_in saddr;
bzero(&saddr,sizeof(saddr));
saddr.sin_family=AF_INET;
saddr.sin_port=htons(7777);
saddr.sin_addr.s_addr=inet_addr("192.168.9.253")；
fd_set rfds,fds;
FD_ZERO(&rfds);
FD_SET(0,&rfds);
FD_SET(sockfd,&rfds);
int nfds=sockfd+1;
int i=0;
int ret=bind(sockfd,(struct sockaddr*)&saddr,sizeof(saddr));
if(ret==-1)
{
perror("bind");
close(sockfd);
return -1;
}
char buf[SIZE]={0};
while(1)
{
fds=rfds;
select(nfds,&fds,NULL,NULL,NULL);
for(i=0;i<nfds;i++)
{
if(FD_ISSET(i,&fds))
{
if(i==0)
{
bzero(&buf,sizeof(buf));
fgets(buf,sizeof(buf)-1,stdin);
buf[strlen(buf)-1]='\0';
}else if(i==sockfd)
{
struct sockaddr dest;
socklen_t len=sizeof(dest);
ret=recvfrom(i,buf,sizeof(buf),0,(struct sockaddr*)&dest,&len);
if(ret==-1)
{
perror("recvfrom");
close(sockfd);
return -1;
}
sendto(i,&buf,sizeof(buf),0,(struct sockaddr*)&dest,len);
printf("buf=%s\n",buf);
FD_SET(i,&rfds);
nfds=nfds>i+1? nfds:i+1;
}
}
}
}
close(i);
return 0;
}
客户端程序：
#define SIZE 32
int main()
{
int sockfd=socket(AF_INET,SOCK_DGRAM,0);
if(sockfd==-1)
{
perror("socket");
return -1;
}
char buf[SIZE]={0};
struct sockaddr_in caddr;
caddr.sin_family=AF_INET;
caddr.sin_port=htons(7777);
caddr.sin_addr.s_addr=inet_addr("192.168.9.253");
fd_set rfds,fds;
FD_ZERO(&rfds);
FD_SET(0,&rfds);
FD_SET(sockfd,&rfds);
do{
fds=rfds;
select(4,&fds,NULL,NULL,NULL);
if(FD_ISSET(0,&fds))
{
bzero(&buf,sizeof(buf));
fgets(buf,sizeof(buf),stdin);
printf("-------\n");
int ret=sendto(sockfd,&buf,sizeof(buf),0,(struct sockaddr*)&caddr,sizeof(caddr));
if(ret==-1)
{
perror("sendto");
close(sockfd);
return -1;
}
printf("------->>>>>>>>>>s\n");
//write(sockfd,buf,sizeof(buf));
}
else if(FD_ISSET(sockfd,&fds))
{
bzero(&buf,sizeof(buf));
recvfrom(sockfd,&buf,sizeof(buf),0,NULL,NULL);
printf("buf=%s\n",buf);
}
}while(0!=strncmp(buf,"quit",4));
close(sockfd);
return 0;
}