Linux网络编程——UDP通信（文件传输）

实验二 UDP数据发送与接收

【实验目的】

1、熟练掌握套接字函数的使用方法。

2、应用套接字函数完成基本UDP通讯，实现服务器与客户端的文件传送

【实验学时】

    4学时

【实验内容】

要求：

（1）客户可以从服务器下载文件、或向服务器上传文件。

（2）客户可向服务器发送多种指令：DOWNLOAD、UPLOAD、YES、NO、START、END、SHUTDOWN、CONTENT、OKDOWLOAD格式：DOWLOAD [filename]表示从服务器下载filename文件，如果服务器存在该文件，返回YES，否则返回NO；客户接收如果是YES，可发送START表示开始下载，之后，服务器将文件传送给客户，客户接收并保存；UPLOAD格式：UPLOAD [filename]表示向服务器上传filename文件，服务器发送NO表示拒绝接收。服务器发送START表示开始传送，之后向服务器传输文件；END:表示文件传送结束SHUTDOWN:表示通讯结束，双方退出。

实验流程如下：

protocol.h:

#ifndef _protocol
#define _protocol

#define INFOLEN 1000
#define SHUTDOWN 0
#define DOWNLOAD 1
#define UPLOAD 2
#define YES 3
#define NO 4
#define START 5
#define END 6
#define CONTENT 7
#define OK 8

struct protocol
{
	int command;
	int len;  //length of buf
	int no;
	char buf[INFOLEN];
};
#endif

server:

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<unistd.h>
#include"protocol.h"


int main()
{
	int sockfd;

	struct sockaddr_in server;
	struct sockaddr_in client;
	int len=sizeof(client);

	int port;
	char ip[20];

	//sock
	sockfd=socket(AF_INET, SOCK_DGRAM, 0);

	printf("client ip: ");
	scanf("%s", ip);
	printf("server port: ");
	scanf("%d", &port);

	bzero(&server, sizeof(server));
	server.sin_family=AF_INET;
	server.sin_port=htons(port);
	server.sin_addr.s_addr=inet_addr(ip);

	//bind
	bind(sockfd, (struct sockaddr *)&server, sizeof(server));

	//sendto/recvfrom
	struct protocol pro;
	while(1)
	{
		int a;
		int num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len);
		printf("command= %d
",pro.command);
		int i=pro.command;
		switch(i)
		{
			case 1:
				a=access(pro.buf,F_OK);
				if(a!=-1)
				{
					pro.command=3;
					sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
					num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len);
					if(pro.command==5)
					{
						FILE *fd;
						pro.no=0;
						fd=fopen(pro.buf,"r+");
						if(fd==NULL)
						{
							perror("create file error");
							exit(1);
						}
						else
						{
							int f;
							while((f=fread(pro.buf,1,1000,fd)) !=0)
							{
								pro.command = 7;
								pro.len=f;
								sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
								pro.no++;
								bzero(&pro.buf,1000);
							}
							bzero(&pro.buf,1000);
							pro.command = 6;
							sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
						}
					}
				}
				else
				{
					printf("no such file!
");
				}
			case 2:
				num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len);	

				pro.command=3;
				int no=0;

				sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));

				FILE *fd;
				fd=fopen(pro.buf,"w+");

				if(fd==NULL)
				{
					perror("create file error");
					exit(1);
				}
				else{
					while((num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len))>0)
					{
						if(pro.command==7&&pro.no==no)
						{
							fwrite(pro.buf,1,pro.len,fd);
							no++;
						}
						else if(pro.command==6)
						{
							break;
						}
						bzero(&pro.buf,1000);
					}

							
				}	
				fclose(fd);	
				break;
		}
	}

	//close
	close(sockfd);

	return 0;
}

client:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include "protocol.h"

int main()
{
	int sockfd;

	struct sockaddr_in server;

	int len=sizeof(server);

	int port;
	char ip[20];

	//sock
	if((sockfd=socket(AF_INET,SOCK_DGRAM,0))==-1)
	{
		perror("socket error");
		exit(1);
	}
	printf("server ip:"); 
	scanf("%s",ip);
	printf("server port:");
	scanf("%d",&port);

	bzero(&server,sizeof(server));
	server.sin_family=AF_INET;
	server.sin_port=htons(port);
	server.sin_addr.s_addr=inet_addr(ip);

	//sendto/recvfrom
	char buf[100];
	int num;
	while(1)
	{
		printf("------------------------------
");
		printf("--------input a number--------
");
		printf("--------1:DOWNLOAD------------
");
		printf("--------2:UPLOAD--------------
");
		printf("--------3:SHUTDOWN------------
");
		printf("------------------------------
");
		int s;
		char p[10];
		printf("input you switch :");
		scanf("%d",&s);
		int shut=0;
		struct protocol pro;
		switch(s)
		{
			case 1:
				printf("input download filename:");
				scanf("%s",pro.buf);
				pro.command=1;
				sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
				num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len);
				if(pro.command==3)
				{
					pro.command=5;
					sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
					FILE *fd;
					fd=fopen(pro.buf,"w+");
					int no=0;
					if(fd==NULL)
					{
						perror("create file error");
						exit(1);
					}
					else
					{
						bzero(&pro.buf,1000);
						while((num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len))>0)
						{	
							if(pro.command==7&&pro.no==no)
							{
								fwrite(pro.buf,1,pro.len,fd);
							}
							else if(pro.command==6)
							{
								printf("file downover
");
								break;
							}
							no++;
						}
					}
					fclose(fd);
				}
				else
					printf("from server:no file
");
				break;
			case 2:
				len=sizeof(server);
				bzero(&pro.buf,1000);
				printf("input Upload filename:");
				scanf("%s",pro.buf);
				pro.command=2;
				sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
				num=recvfrom(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server,&len);
				printf("command %d
",pro.command);
				if(pro.command==3)
				{
					FILE *fd;
					pro.no=0;
					fd=fopen(pro.buf,"r+");
					if(fd==NULL)
					{
						perror("create file error");
						exit(1);
					}
					else
					{
						int f;
						bzero(&pro.buf,1000);
						while((f=fread(pro.buf,1,1000,fd))!=0)
						{	
							pro.command=7;
							pro.len=f;
							sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));
							pro.no++;
						}
						pro.command=6;
						sendto(sockfd,(struct protocol *)&pro,sizeof(struct protocol),0,(struct sockaddr *)&server ,sizeof(server));


					}
					fclose(fd);		
				}
				break;
			case 3:
				exit(1);
				break;
			default:
				printf("input a right number
");
		}
	}
	close(sockfd);
	return 0;
}

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