#include <stdio.h>#include <stdlib.h>#include <errno.h>#include <string.h>#include <netdb.h>#include <fcntl.h>#include <sys/time.h>#include <sys/types.h>#include <netinet/in.h>#include <sys/socket.h>#include <unistd.h>#include <time.h>#include <resolv.h>#define SERVPORT 3333#define MAXDATASIZE 80int main(int argc,char *argv[]){	int sockfd,sendbytes,recvbytes;	int maxfd;	int ffd;	int ret;	int i;	char buf[MAXDATASIZE];	char recvbuf[MAXDATASIZE];	struct timeval tv;	struct hostent *host;	struct sockaddr_in serv_addr;	fd_set rfds;		if(argc < 2)	{		fprintf(stderr,"Please enter the server's hostname!\n");		exit(1);	}	if((host=gethostbyname(argv[1]))==NULL)	{		perror("gethostbyname");		exit(1);	}	if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)	{		perror("socket");		exit(1);	}		serv_addr.sin_family=AF_INET;	serv_addr.sin_port=htons(SERVPORT);	serv_addr.sin_addr=*((struct in_addr *)host->h_addr);	bzero(&(serv_addr.sin_zero),8);		if(connect(sockfd,(struct sockaddr *)&serv_addr,\		sizeof(struct sockaddr))==-1)	{		perror("connect");		exit(1);	}		while(1)	{		FD_ZERO(&rfds);		FD_SET(0,&rfds);		maxfd=0;		FD_SET(sockfd,&rfds);		if(maxfd<sockfd)		{			maxfd=sockfd;		}			tv.tv_sec=1;		tv.tv_usec=0;				ret=select(maxfd+1,&rfds,NULL,NULL,&tv);				if (ret==-1)		{			perror("select error:\n");			exit(1);		}		else if (ret==0)		{			continue;		}		else		{			if (FD_ISSET(0,&rfds))			{				fgets(buf,10,stdin);				sendbytes=send(sockfd,buf,sizeof(buf),0);				if(sendbytes==-1)				{					perror("send error");					exit(1);				}				for(i=strlen(buf);i>=0;i--)				{					buf[i+2]=buf[i];				}				buf[0]='.';				buf[1]='/';				//break;			}			if(FD_ISSET(sockfd,&rfds))			{				recvbytes=recv(sockfd,recvbuf,MAXDATASIZE,0);				if(recvbytes==-1)				{					perror("recv file");					exit(1);				}				ffd=open("./newfile",O_WRONLY|O_CREAT,0600);				if(ffd==-1)				{					printf("create file error\n");					exit(1);				}				write(ffd,recvbuf,MAXDATASIZE);				memset(recvbuf,0,sizeof(recvbuf));				break;			}		}	}	close(sockfd);	return 0;}