//File Name: Client.c
//客戶程序發(fā)送報(bào)文,然后接收主機(jī)交換IP地址和UDP端口號(hào)的報(bào)文
//命令行格式:client 主機(jī)名 端口號(hào)
#include "winsock.h"
#include "stdio.h"
#pragma comment(lib,"wsock32")


main( int argc, char *argv[] )
{
	WSADATA WSAData;
	int sock;
	struct sockaddr_in cliaddr;
	struct sockaddr_in srvaddr;
	struct hostent *hp;
	char send_message[100];
	char recv_message[100];

	//命令行參數(shù)不能少于4個(gè)(client 主機(jī)名 端口號(hào) 消息字符串)
	if ( argc < 4 )
	{
		printf("usage: client server_host server_port msg_string\n");
		exit(0);
	} 

	//初始化Ws2_32.dll
	WSAStartup(MAKEWORD(1,1),&WSAData);

	//建立套接字
	sock = socket( AF_INET, SOCK_STREAM, 0 );
	if ( sock < 0 ) 
	{
		perror( "opening stream socket" );
		exit( 1 );
	}
	
	//創(chuàng)建地址
	cliaddr.sin_family = AF_INET;
	cliaddr.sin_addr.s_addr = 0x7F000001;
	srvaddr.sin_family = AF_INET;

	//得到服務(wù)器名
	hp = gethostbyname( argv[1] );
	if ( hp == 0 ) {
		fprintf( stderr, "%s: unknown host\n", argv[1] );
		exit( 3 );
	}

	//連接服務(wù)器
	memcpy( (char *)&srvaddr.sin_addr, (char *)hp->h_addr, hp->h_length );
	srvaddr.sin_port = atoi(argv[2]);
	if ( connect( sock, (struct sockaddr *)&srvaddr, sizeof(srvaddr) ) < 0 ) {
		perror( "connecting stream socket" );
		exit( 4 );
	}

	//發(fā)送消息到服務(wù)器
	strcpy( send_message, argv[3] );
	
	if (send(sock, send_message, 100, 0) < 0) perror("send");

	//從服務(wù)器接收消息
	if ( recv(sock, recv_message, 100, 0) < 0) perror("recv");
	printf("receive: %s\n", recv_message);
	
	//關(guān)閉套接字	
	closesocket( sock );
	exit( 0 );
}