client.c

socket通信模型

#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#define PORT 1234
#define MAXSOCKFD 10

/*客户端主函数*/
int main()
{
	int sockfd;
	int newsockfd;
	int is_connected[MAXSOCKFD];
	int fd;
	struct sockaddr_in addr;
	int addr_len = sizeof(struct sockaddr_in);
	fd_set readfds;
	char buffer[256];
	char msg[ ] ="Welcome to server!";
	
	/*创建套接字*/
	if ((sockfd = socket(AF_INET,SOCK_STREAM,0))<0)
	{
		perror("socket");
		exit(1);
	}

	bzero(&addr,sizeof(addr));
	addr.sin_family =AF_INET;
	addr.sin_port = htons(PORT);
	addr.sin_addr.s_addr = htonl(INADDR_ANY);

	if(bind(sockfd,(struct sockaddr *)&addr,sizeof(addr))<0){
		perror("connect");
		exit(1);
	}

	if(listen(sockfd,3)<0){
		perror("listen");
		exit(1);
	}
	
	for(fd=0;fd<MAXSOCKFD;fd++)
		is_connected[fd]=0;

	while(1){
		FD_ZERO(&readfds);
		FD_SET(sockfd,&readfds);
		
		for(fd=0;fd<MAXSOCKFD;fd++)
			if(is_connected[fd]) FD_SET(fd,&readfds);

		if(!select(MAXSOCKFD,&readfds,NULL,NULL,NULL))continue;
		for(fd=0;fd<MAXSOCKFD;fd++)
			if(FD_ISSET(fd,&readfds)){
				if(sockfd == fd){
					if((newsockfd = accept (sockfd,(struct sockaddr *)&addr,(socklen_t*)&addr_len))<0)
						perror("accept");
					write(newsockfd,msg,sizeof(msg));
					is_connected[newsockfd] =1;
					printf("cnnect from %s\n",inet_ntoa(addr.sin_addr));
				}else{
					bzero(buffer,sizeof(buffer));
					if(read(fd,buffer,sizeof(buffer))<=0){
						printf("connect closed.\n");
						is_connected[fd]=0;
						close(fd);
					}else
					printf("%s",buffer);
				}
			}
	}
}