WinSock网络编程学习笔记（九）：基于UDP实现DayTime协议

#include<stdio.h>
#include<winsock2.h>

#pragma comment(lib,"ws2_32.lib")	//winsock 使用的库函数

#define DAY_TIME_DEF_PORT 13		//默认端口	
#define DAY_TIME_BUF_SIZE 64		//缓冲区大小
#define DAY_TIME_DEF_COUNT 2		//发送的次数

int main(int argc , char **argv)
{
	WSADATA wsaData;
	SOCKET time_soc = 0;
	struct  sockaddr_in  peer_addr,serv_addr;
	int timeout = 2000;				//接收超时，2s
	int i,
		result,
		send_len,
		addr_len = sizeof(serv_addr);
	char *dest = "127.0.0.1",
		 *send_data = "Hello,DayTime!";
	char recv_buf[ DAY_TIME_BUF_SIZE ];

	if(argc == 2)
		dest = argv[1];
	WSAStartup(WINSOCK_VERSION,&wsaData);			//初始化Winsock资源
	send_len = strlen(send_data);
	//填写服务器地址
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(DAY_TIME_DEF_PORT);
	serv_addr.sin_addr.s_addr = inet_addr(dest);	//当然是转网络字节序
	//错误判断，都是程序化的步骤（套路）...
	if(serv_addr.sin_addr.s_addr == INADDR_NONE)
	{
		printf("[DayTime]invaild address\r\n");
		return -1;
	}
	//创建DayTime使用的Socket，注意是 “SOCK_DGRAM”类型，协议为：UDP：无连接、不可靠的传输服务
	time_soc = socket(AF_INET,SOCK_DGRAM,0);
	
	result = setsockopt(time_soc,SOL_SOCKET,SO_RCVTIMEO,(char *)&timeout,sizeof(timeout));
	/*设置接收数据的超时值，这样做的目的是，一旦数据丢失，客户端不会收到服务器的数据。
	  客户端使用的是阻塞套接口，程序永远阻塞在 recvfrom函数，无法进行其他处理。
	  设置超时时间后，recvfrom函数会返回SOCKET_ERROR,程序会继续执行，重发数据。
	*/
	/*
	UDP是不可靠的,下面使用循环，设置的是消息发送两次，
	*/
	for(i = 0;i<DAY_TIME_DEF_COUNT;i++)
	{	//发送数据
		result = sendto( time_soc,send_data,send_len,0,(struct sockaddr*)&serv_addr,sizeof(serv_addr));
		//接收应答
		result = recvfrom( time_soc , recv_buf , DAY_TIME_BUF_SIZE , 0 , (struct sockaddr*)&peer_addr , &addr_len);
		if(result >= 0)
		{
			recv_buf[result] = 0;
			printf( " [Daytime]recv: \"%s\" ,from : %s\r\n" , recv_buf , inet_ntoa(peer_addr.sin_addr) );
		}
	}
	closesocket(time_soc);
	WSACleanup();
	return 0;
}

#include<stdio.h>
#include<winsock2.h>
#include<time.h>

#pragma comment(lib,"ws2_32.lib")

#define DAY_TIME_DEF_PORT 13
#define DAY_TIME_BUF_SIZE 64
#define DAY_TIME_DEF_COUNT 2

int main(int argc , char **argv)
{
	WSADATA wsaData;
	SOCKET serv_sock = 0;
	struct  sockaddr_in  serv_addr,		//服务器端句柄
						 clnt_addr;		//客户端句柄
	unsigned short port = DAY_TIME_DEF_PORT;
	int result,
		addr_len = sizeof(serv_addr);
	char *time_str,
		 recv_buf[ DAY_TIME_BUF_SIZE ];
	time_t now_time;
	WSAStartup(WINSOCK_VERSION,&wsaData);	//初始化
	if(argc == 2)
		port = atoi(argv[1]);
	serv_sock = socket(AF_INET,SOCK_DGRAM,0);
	//
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(port);
	serv_addr.sin_addr.s_addr =	INADDR_ANY;
	//调用bind为套接口绑定本地地址

	result = bind(serv_sock,(struct sockaddr *)&serv_addr,addr_len);
	if( result == SOCKET_ERROR)
	{
		printf("[Daytime]bind error : %d",WSAGetLastError());
		closesocket(serv_sock);
		return -1;
	}
	printf("[Daytime] the server is running...\n");
	while(1)
	{
		result = recvfrom( serv_sock , recv_buf , DAY_TIME_BUF_SIZE , 0 , (struct sockaddr*)&clnt_addr , &addr_len);
		if(result >= 0)	//表示收到对方数据
		{
			recv_buf[result] = 0;
			printf( " [Daytime]recv: \"%s\" ,from : %s\r\n" , recv_buf , inet_ntoa(clnt_addr.sin_addr) );
			now_time = time(0);			//得到当前时间
			time_str = ctime(&now_time);//转字符串
			//向客户端发送当前的日期和时间字符串
		    sendto( serv_sock,time_str,strlen(time_str),0,(struct sockaddr*)&clnt_addr , addr_len);
		}
	}
	closesocket(serv_sock);
	WSACleanup();
	return 0;


}