//File Name: server.c
//服務器程序接收到連接,它顯示接收到的報文所包含的字符串
//并且把報文的內容拷貝到新的字符串,再發送出去,這時相當于交換了IP地址和UDP端口號
//命令行格式:server 端口號

#include "winsock.h"
#include "stdio.h"
#define TRUE 1
#pragma comment(lib,"wsock32")

main( int argc, char *argv[] )
{
	WSADATA WSAData;
	int sock;
	int msgsock;
	struct sockaddr_in cliaddr;
	struct sockaddr_in srvaddr;
	int addrlen;
	char send_message[100];
	char recv_message[100];
	
	//命令行參數不能少于2個(server 端口號)
	if (argc < 2)
	{
		printf("usage: server server_port\n");
		exit(0);
	} 
	//初始化Ws2_32.dl
	WSAStartup(MAKEWORD(1,1),&WSAData);

	//創建套接字
	sock = socket( AF_INET, SOCK_STREAM, 0 );
	if ( sock < 0 ) {
		perror( "opening stream socket" );
		exit( 1 );
	}

	//創建地址,端口號
	srvaddr.sin_family = AF_INET;
	srvaddr.sin_addr.s_addr = INADDR_ANY;
	srvaddr.sin_port = atoi(argv[1]);
	
	//把本地地址綁定到創建的套接字上
	if ( bind(sock, (struct sockaddr *)&srvaddr, sizeof(srvaddr)) < 0 ) {
		perror( "binding stream socket" );
		exit( 2 );
	}

	//開始監聽端口
	if ( listen( sock, 5 ) < 0 ) 
	{
		perror( "listening stream socket" );
		exit( 3 );
	}
	
	while( 1 ) {
		//等待接收連接
		addrlen = sizeof(cliaddr);
		msgsock = accept( sock, (struct sockaddr *)&cliaddr, (int *)&addrlen );
		if ( msgsock == -1 )
		{
			perror( "accept" );
			exit( 4 );
		}

		//從客戶機接收消息
		if ( recv(msgsock, recv_message, 100, 0) < 0 ) 
		{
			perror( "reading stream message" );
			exit( 5 );
		}

		//把收到的報文消息打印出來
		printf("receive: %s\n", recv_message);

		//把收到的報文消息拷貝下來	
		strcpy( send_message, "message (" );
		strcat( send_message, recv_message );
		strcat( send_message, ") has received!" );

		//發送消息到客戶機
		if ( send(msgsock, send_message, 100, 0) < 0) 
		{
			perror("send");
			exit( 6 );
		}
		
		//關閉消息套接字
		closesocket( msgsock );
	} 
	
	//關閉套接字
	closesocket( sock );
	WSACleanup();

	exit( 0 );
}