linux网络环境下socket套接字编程（UDP文件传输）

今天我们来介绍一下在linux网络环境下使用socket套接字实现两个进程下文件的上传，下载，和退出操作！

在socket套接字编程中，我们当然可以基于TCP的传输协议来进行传输，但是在文件的传输中，如果我们使用TCP传输，会造成传输速度较慢的情况，所以我们在进行文件传输的过程中，最好要使用UDP传输。

在其中，我们需要写两个程序，一个客户端，一个服务端，在一个终端中，先运行服务端，在运行客户端，在服务端和客户端都输入IP地址和端口号，注意服务端和客户端的端口号要相同，然后选择功能，在linux网络编程中，使用UDP进行传输属于比较简单的操作，所以直接上代码吧，详细的讲解我将会在之后上传！

client（客户端）：

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

     /*--------------------------*/
     int socketfd ;
     int addrlen;
     struct sockaddr_in server;
     struct protocol sentbuf;
     struct protocol recvbuf;
     int num;
     char ip[];
     int port;
     int choice ;
     char filename[];

     /*--------------------------*/
     void ShowMenu();
     void DownLoad();
     void UpLoad();
     void ShutDown();

     int main(){
     /*---------------------------*/
         socketfd = socket(AF_INET , SOCK_DGRAM ,  );
         if(socketfd == -){
             perror("socket failed!\n");
             exit();
         }
     /*---------------------------*/
         printf("please input ip of server:\n");
         scanf("%s",ip);
         printf("please input port of server:\n");
         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);
         addrlen = sizeof(server);
     /*---------------------------*/
         while(){
             ShowMenu();
             scanf("%d",&choice);
             if(choice == DOWNLOAD){
                 printf("client download!\n");
                 DownLoad();
             }
             else if(choice == UPLOAD){
                 UpLoad();
             }
             else if(choice == SHUTDOWN){
                 printf("client shutdown!\n");
                 ShutDown();
                 break;
             }
             else{
                 printf("please input the right choice!\n");
             }
         }
         close(socketfd);
         return ;
     }

     void ShowMenu(){
         printf("please make a choice:\n");
         printf("0:shutdown!\n");
         printf("1:download!\n");
         printf("2:upload!\n");
     }

     void DownLoad(){
         bzero(&recvbuf , sizeof(recvbuf));
         bzero(&sentbuf , sizeof(sentbuf));
         bzero(filename , sizeof(filename));
         printf("please input the filename:\n");
         scanf("%s",sentbuf.buf);
         sentbuf.command = DOWNLOAD;
         sendto(socketfd , &sentbuf , sizeof(sentbuf),  , (struct sockaddr*)&server , sizeof(server));
         bcopy(sentbuf.buf , filename , sizeof(sentbuf.buf));
         recvfrom(socketfd  , &recvbuf , sizeof(recvbuf) ,  , (struct sockaddr*)&server , &addrlen);
         printf("recvbuf:%d\n",recvbuf.command);
         if(recvbuf.command == YES){
             printf("YES!\n");
             int choice_1;
             printf("if you input a 5 , the file transmission start!\n");
             scanf("%d",&choice_1);
             if(choice_1 == START){
                 sentbuf.command = START;
                 sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&server , sizeof(server));
                 int no =  ;
                 int fd = open(filename , O_CREAT | O_TRUNC | O_WRONLY ,  );
                 if(fd < ){
                     perror("creat file is failed!\n");
                     exit();
                 }
                 bzero(&recvbuf , sizeof(recvbuf));
                 while( ( num = recvfrom(socketfd , &recvbuf , sizeof(recvbuf) ,  , (struct sockaddr*)&server , &addrlen)) > ){
                     if( recvbuf.command == CONTENT ){
                         if(no == recvbuf.no){
                             write(fd , recvbuf.buf , recvbuf.len);
                             bzero(&recvbuf , sizeof(recvbuf));
                         }
                         else{
                             perror("The file no is not same,  Some massage is missed!error occured!\n");
                             break;
                         }
                     }
                     if( recvbuf.command == END){
                         close(fd);
                         printf("transmission is successful!\n");
                         break;
                     }
                 }
             }
         }
         else if(recvbuf.command == NO){
             perror("No such file on server!\n");
         }
         else{
             perror("recvbuf.command error!\n");
             exit();
         }
     }

     void ShutDown(){
         sentbuf.command = SHUTDOWN;
         sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&server , sizeof(server));
         printf("client is end!\n");
     }

     void UpLoad(){
         bzero(&recvbuf , sizeof(recvbuf));
         bzero(&sentbuf , sizeof(sentbuf));
         bzero(filename , sizeof(filename));
         printf("please input you want to upload filename:\n");
         scanf("%s",sentbuf.buf);
         sentbuf.command = UPLOAD;
         sendto(socketfd , &sentbuf , sizeof(sentbuf),  , (struct sockaddr*)&server , sizeof(server));
         bcopy(sentbuf.buf , filename , sizeof(sentbuf.buf));
         int fd ;
         fd = open(filename , O_RDONLY);
         if(fd < ){
             perror("The file is not exist!\n");
             exit();
         }
         recvfrom(socketfd , &recvbuf , sizeof(recvbuf),  , (struct sockaddr*)&server , &addrlen);
         if( recvbuf.command == START ){
             int no =  ;
             while( ( num = read(fd , sentbuf.buf , INFOLEN)) >  ){
                 sentbuf.no = no ;
                 sentbuf.command = CONTENT;
                 sentbuf.len = strlen(sentbuf.buf);
                 sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&server,sizeof(server));
                 no++;
                 bzero(&sentbuf , sizeof(sentbuf));
             }
             bzero(&sentbuf , sizeof(sentbuf));
             sentbuf.command = END;
             sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&server , sizeof(server));
         }
         else if(recvbuf.command == NO){
             printf("not transmission!\n");
         }
         else{
             perror("error! wrong choice!\n");
         }
     }

server（服务端）：

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

 int socketfd;
 int addrlen;
 struct sockaddr_in server;
 struct sockaddr_in client;
 struct protocol sentbuf;
 struct protocol recvbuf;
 int num;
 char ip[];
 int port;
 int choice;
 char filename[];

 void DownLoad();
 void ShutDown();
 void UpLoad();

 int main(){
     socketfd = socket( AF_INET , SOCK_DGRAM ,  );
     if( socketfd == -){
             perror("socket failed!\n");
             exit();
     }

     printf("please input client ip:\n");
     scanf("%s" , ip);
     printf("please input client port:\n");
     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);

     int bin = bind(socketfd , (struct sockaddr*)&server , sizeof(server));
     if(bin == -){
         perror("bind failed!\n");
         exit();
     }

     addrlen = sizeof(client);
     //char filename[100];

     while(){
         bzero(&recvbuf , sizeof(recvbuf));
         num = recvfrom(socketfd , &recvbuf , sizeof(recvbuf) ,  , (struct sockaddr*)&client , &addrlen);
         choice = recvbuf.command;
         bcopy(recvbuf.buf ,filename, sizeof(recvbuf.buf));
         printf("%s\n",filename);
         if(choice == DOWNLOAD){
             printf("kkkkkkkk\n");
             DownLoad();
         }
         else if(choice == SHUTDOWN){
             printf("server will shutdown!\n");
             ShutDown();
             break;
         }
         else if(choice == UPLOAD){
             UpLoad();
         }
     }
     return ;
 }

 void DownLoad(){
     char buf[];
     int fd ;
     printf("11111\n");
     printf("%s\n",filename);
     fd = open((filename) , O_RDONLY);
     printf("fd:%d\n",fd);
     bzero(&sentbuf , sizeof(sentbuf));
     if(fd < ){
         sentbuf.command = NO;
         sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&client , sizeof(client));
         printf("no such file!\n");
         exit();
     }
     else{
         sentbuf.command = YES;
         printf("YES!\n");
         sendto(socketfd , &sentbuf, sizeof(sentbuf) ,  , (struct sockaddr*)&client , sizeof(client));
         recvfrom(socketfd , &recvbuf , sizeof(recvbuf) ,  , (struct sockaddr*)&client , &addrlen);
         if(recvbuf.command == START){
             int no =  ;
             while((num = read(fd , sentbuf.buf , INFOLEN)) > ){
                 sentbuf.no = no ;
                 sentbuf.command = CONTENT;
                 sentbuf.len = strlen(sentbuf.buf);
                 sendto(socketfd , &sentbuf , sizeof(sentbuf),,(struct sockaddr*)&client , sizeof(client));
                 no++;
                 bzero(&sentbuf , sizeof(sentbuf));
             }
             bzero(&sentbuf , sizeof(sentbuf));
             sentbuf.command = END;
             sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&client , sizeof(client));
         }
     }
 }

 void ShutDown(){
     printf("Now server is shutdown!\n");
 }

 void UpLoad(){
         //bzero(&recvbuf , sizeof(recvbuf));
         bzero(&sentbuf , sizeof(sentbuf));
         bzero(&filename , sizeof(filename));
         //recvfrom(socketfd , &recvbuf , sizeof(recvbuf) , 0 , (struct sockaddr*)&client , &addrlen);
         printf("4:NO 5:START\n");
         scanf("%d" , &sentbuf.command);
         sendto(socketfd , &sentbuf , sizeof(sentbuf) ,  , (struct sockaddr*)&client , sizeof(client));
         if( sentbuf.command == START){
             int no =  ;
             printf("filename:%s\n",recvbuf.buf);
             int fd = open(recvbuf.buf , O_CREAT | O_TRUNC | O_WRONLY ,  );
             if(fd < ){
                 perror("create file failed!\n");
                 exit();
             }
             bzero(&recvbuf , sizeof(recvbuf) );
             while(( num = recvfrom(socketfd , &recvbuf , sizeof(recvbuf) ,  , (struct sockaddr*)&client , &addrlen)) > ){
                 if( recvbuf.command == CONTENT ){
                     if( no == recvbuf.no ){
                         write(fd , recvbuf.buf , recvbuf.len);
                         bzero(&recvbuf , sizeof(recvbuf));
                     }
                     else{
                         perror("The file no is not same . Some massage is missed!\n");
                         break;
                     }
                 }
                 if( recvbuf.command == END ){
                     close(fd);
                     printf("transmission is successful!\n");
                     break;
                 }
             }
         }
         else if( sentbuf.command == NO ){
             printf("The file can't transmission!\n");
         }
         else{
             perror("please input right choice!\n");
             exit();
         }
 }

makefile：

main:udpserver.o udpclient.o
    gcc -o udpserver udpserver.o
    gcc -o udpclient udpclient.o
udpserver.o:udpserver.c
    gcc -c udpserver.c
udpclient.o:udpclient.c
    gcc -c udpclient.c