多客户模式

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

int main(int argc, char const *argv[])
{
	int server_sockfd, client_sockfd;
	int server_len, client_len;
	struct sockaddr_in server_address;
	struct sockaddr_in client_address;
	int result;
	fd_set readfds,testfds;

	// create a socket for server and name it
	server_sockfd=socket(AF_INET,SOCK_STREAM,0);

	server_address.sin_family=AF_INET;
	server_address.sin_addr.s_addr=htonl(INADDR_ANY);
	server_address.sin_port=htons(9734);
	server_len=sizeof(server_address);

	//bind the socket and address
	bind(server_sockfd,(struct sockaddr*)&server_address,server_len);

	listen(server_sockfd,5);

	FD_ZERO(&readfds);
	FD_SET(server_sockfd,&readfds);

	while(1){
		char ch;
		int fd;
		int nread;

		testfds=readfds;
		printf("server waiting...\n");

		result=select(FD_SETSIZE,&testfds,(fd_set*)NULL,(fd_set*)NULL,(struct timeval*)0);

		if(result<1){
			perror("server5...");
			exit(1);
		}

		for(fd=0;fd<FD_SETSIZE;fd++){
			if(FD_ISSET(fd,&testfds)){
				if(fd==server_sockfd){
					client_len=sizeof(client_address);
					client_sockfd=accept(server_sockfd,(struct sockaddr*)&client_address,&client_len);
					FD_SET(client_sockfd,&readfds);
					printf("adding client on fd %d\n", client_sockfd );
				}else{
					ioctl(fd,FIONREAD,&nread);

					if(nread==0){
						close(fd);
						FD_CLR(fd,&readfds);
						printf("removing client on fd %d\n",fd );
					}else{
						read(fd,&ch,1);
						sleep(3);
						printf("server client on fd %d\n",fd );
						ch++;
						write(fd,&ch,1);
					}
				}
			}
		}
	}

	return 0;
}