client.c.txt

LINUX网络编程文档

/* Examples for Linux Network Programming----client.c */
#ifndef unix
#define WIN32
#include <windows.h>
#include <winsock.h>
#else
#define closesocket close
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/inet.h>
#include <arpa/inet.h>
#include <netdb.h>
#endif

#include <stdio.h>
#include <string.h>

#define PROTORORT 5193		/* default protocol port number */

extern int error;
char localhost[] = "localhost";		/*default host name */
/*-----------------------------------------------------------
*Program: client
*Purpose: allocate a socket,connect to a server, and print all output
*Syntax: client[host[port]]
*		host - name of a computer on which server is executing
*		port - protocol port number server is using
*
*Notes: Both arguments are optional. If no host name is specified,the 
*	client uses "localhost"; If no protocol port is specified,the
*	client uses the default given by PROTOPORT.
*-----------------------------------------------------------
*/
main(argc,argv)
int argc;
char *argv[];
{
  struct	hostent *ptrh;		/*pointer to a host table entry*/
  struct	protoent *ptrp;		/*pointer to a protocol table entry*/
  struct	sockaddr_in sad;	/*structure to hold server's address*/
  int		sd;			/*socket descriptor*/
  int 		port;			/*protocol prot number*/
  char		*host;			/*pointer to host name*/
  int 		n;			/*number of characters read*/
  char		buf[1000];		/*buffer for data from the server */
  #ifdef WIN32
  	WSADATA wsaData;
  	WSAStartup(0x0101, &wsaData);
  #endif
  memset((char *)&sad,0,sizeof(sad));	/*clear sockaddr structure*/
  sad.sin_family = AF_INET;		/*set family to Internet */
  /*Check command- line argument for portocol port and extract */
  /*port number if one is specifie. Otherwise, use the default*/
  /*port value given by constant PROTOPORT */
  if(argc >2){			/*if protocol port specified*/
  	port = atoi(argv[2]);	/*convert to binary */
  }else{
  	port = PROTOPORT;	/*use default port number*/
  }
  if(port>0)			/*test for legal value*/
  	sad.sin_port = htons(u_short)port);
  				/*print error message and exit */
  else{
  	fprintf(stderr,"bad port number %s\n",argv[2]);
  	exit(1);
  }
  /*Check host argument and assign host name. */
  
  if(argc>1){
  	host = argv[1];	/*if host argument specifie */
  }else{
  	host = localhost;
  }
  /*Convert host name to equivalent IP address and copy to sad*/
  
  ptrh = gethostbyname(host);
  if( ((char *)ptrh) == NULL){
  	fprintf(stderr, "invalid host: %s\n",host);
  	exit(1);
  }
  memcpy(&sad.sin_addr.ptrh->h_addr,ptrh->h_length);
  /*Map TCP transport protocol name to protocol number. */
  
  if( ((int)(ptrp = getprotobyname("tcp"))) ==0{
  fprintf(stderr,"cannot map \ "tcp\" to protocol number);
  exit(1);
 }

 /*Create a socket. */

 sd=socket(AF_INET,SOCK_STREAM,ptrp->p_proto);
 if(sd<0){
	fprintf(stderr,"socket creation failed\n");
	exit(1);
 }
 /*Connect the socket to the specified server.*/

 if(connect(sd,(struct sockaddr *)&sad, size of(sad) <0){
	fprintf(stderr,"connect failed \n");
	exit(1);
 }
 /*Repeatedly read data from socket and write to user'screen.*/

 n=recv(sd,buf,sizeof(buf),0);
 while(n>0){
	write(1,buf,n);
	n=recv(sd,buf,sizeof(buf),0);
 }

 /*Close the socket. */
 closesocket(sd);
 /*Terminate the client program gracefully.*/
 exit(0);
}