/******* 客戶端程序  TCPClient.c ************/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>#include <unistd.h>#include <sys/socketvar.h>#include <arpa/inet.h>
#define RECVBUFSIZE 1024
int main(int argc, char *argv[])
{
 int sockfd;
 char buffer[RECVBUFSIZE];
 struct sockaddr_in server_addr;
 struct hostent *host;
 int portnumber,nbytes;

 if(argc!=3)
 {
  fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
  exit(1);
 }
 
 if((portnumber=atoi(argv[2]))<0)
 {
        fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
        exit(1);
 }
 
/*客戶程序開始建立 sockfd描述符*/
 if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
 {
        fprintf(stderr,"Socket Error:%s\a\n",strerror(errno));
        exit(1);
 }

/*客戶程序填充服務端的資料*/
 bzero(&server_addr,sizeof(server_addr));
 server_addr.sin_family=AF_INET;
 server_addr.sin_port=htons(portnumber);
 server_addr.sin_addr.s_addr=inet_addr(argv[1]);

 /*客戶程序發起連接請求*/ 
 if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1)
{
  fprintf(stderr,"Connect Error:%s\a\n",strerror(errno));
  exit(1);
}

/*連接成功*/
if((nbytes=recv(sockfd,buffer, RECVBUFSIZE,0))==-1)
{
        fprintf(stderr,"Read Error:%s\n",strerror(errno));
        exit(1);
 }
 buffer[nbytes]='\0';
 printf("I have received:%s\n",buffer);
/*結束通訊*/
 close(sockfd);
 exit(0);
}