#include<sys/types.h>#include<sys/socket.h>#include<netinet/in.h>#include<arpa/inet.h>#include<unistd.h>#define PORT 1234#define MAXSOCKFD 10main(){int sockfd,newsockfd,is_connected[MAXSOCKFD],fd;struct sockaddr_in addr;int addr_len = sizeof(struct sockaddr_in);fd_set readfds;char buffer[256];char msg[ ] ="Welcome to server!";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,&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,&addr,&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);}elseprintf("%s",buffer);}}}}