linux应用程序_1_文本浏览器_9_网络打印_2_UDP基本知识和例程

linux应用程序_1_文本浏览器_9_网络打印_2_UDP基本知识和例程

 

UDP(User Datagram Protocol)用户数据报协议是一种非面向连接的协议，这种协议并不能保证我们的网络程序的连接是可靠的，可能出现丢包现象，在视频传输时用的就是UDP协议，传输可能会出现花屏现象，但尽可能保证传输的流畅度

基本调用和TCP类似，

接收要使用recvfrom

发送可以使用sendto或connect + recvfreom

ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags, struct sockaddr *src_addr, socklen_t *addrlen);

ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen);

例程：

server.c

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <netdb.h>



#define BACKLOG 	10
#define SERVER_PORT 8888

int main(int argc,char **argv)
{
	int iServerFd, iClientFd;
	int iRet;

	struct sockaddr_in tSocketServerAddr;
	struct sockaddr_in tSocketClientAddr;

	int iAddrLen = sizeof(struct sockaddr);

	char pcBuf[1024];
	int iLen;
	

	iServerFd = socket(AF_INET, SOCK_DGRAM, 0);
	if(iServerFd < 0)
	{
		printf("socket error\r\n");
		return -1;
	}
	tSocketServerAddr.sin_family        = AF_INET;
	tSocketServerAddr.sin_port          = htons(SERVER_PORT);
	tSocketServerAddr.sin_addr.s_addr   = INADDR_ANY;
		
	memset(tSocketServerAddr.sin_zero, 0, 8);
	iRet = bind(iServerFd, (struct sockaddr *)&tSocketServerAddr, iAddrLen);
	if(iRet < 0)
	{
		printf("bind error\r\n");
		goto error;
	}
	
	while(1)
	{
		iAddrLen = sizeof(struct sockaddr);
		iLen = recvfrom(iServerFd, pcBuf, 1023, 0, (struct sockaddr *)&tSocketClientAddr, &iAddrLen);
		if(iLen > 0)		
		{
			pcBuf[iLen] = '\0';
			printf("get msg %s from Client %s\r\n", pcBuf, inet_ntoa(tSocketClientAddr.sin_addr));
		}

	}

	close(iServerFd);
	return 0;

error:
	close(iServerFd);
	return -1;
}

client.c

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <netdb.h>


#define SERVER_PORT	8888

int main(int argc,char **argv)
{
	int iServerFd, iClientFd;
	int iRet;

	struct sockaddr_in tSocketServerAddr;


	char pcBuf[1024];
	int iLen;

	int i;

	if(argc != 2)
	{
		printf("Usage : %s <server_ip>\r\n", argv[0]);
		return -1;
	}

	
	iClientFd = socket(AF_INET, SOCK_DGRAM, 0);
	if(iClientFd < 0)
	{
		printf("socket error\r\n");
		return -1;
	}
	
	tSocketServerAddr.sin_family = AF_INET;
	tSocketServerAddr.sin_port   = htons(SERVER_PORT);
	if(!inet_aton(argv[1], &tSocketServerAddr.sin_addr))
	{
		printf("ivalid server_ip\r\n");
		goto error;
	}
	memset(tSocketServerAddr.sin_zero, 0, 8);

#ifdef OR
	iRet = connect(iClientFd, (struct sockaddr *)&tSocketServerAddr, sizeof(struct sockaddr));
	if(iRet < 0)
	{
		printf("connect error\r\n");
		return -1;
	}
#endif
	
	while(1)
	{
		if(!fgets(pcBuf, 1023, stdin))
		{
			printf("fgets error\r\n");
			goto error;
		}
#ifdef OR		
		iLen = send(iClientFd, pcBuf, strlen(pcBuf), 0);
#else
		i = sizeof(struct sockaddr);
		iLen = sendto(iClientFd, pcBuf, strlen(pcBuf), 0, (struct sockaddr *)&tSocketServerAddr, i);
#endif
		if(iLen <= 0)
		{
			printf("send error\r\n");
			goto error;
		}
	}

	close(iClientFd);
	return 0;

error:
	close(iClientFd);
	return -1;
}