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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[20]; int port; int choice ; char filename[100]; /*--------------------------*/ void ShowMenu(); void DownLoad(); void UpLoad(); void ShutDown(); int main(){ /*---------------------------*/ socketfd = socket(AF_INET , SOCK_DGRAM , 0 ); if(socketfd == -1){ perror("socket failed!\n"); exit(1); } /*---------------------------*/ 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(1){ 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 0; } 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), 0 , (struct sockaddr*)&server , sizeof(server)); bcopy(sentbuf.buf , filename , sizeof(sentbuf.buf)); recvfrom(socketfd , &recvbuf , sizeof(recvbuf) , 0 , (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) , 0 , (struct sockaddr*)&server , sizeof(server)); int no = 0 ; int fd = open(filename , O_CREAT | O_TRUNC | O_WRONLY , 0644 ); if(fd < 0){ perror("creat file is failed!\n"); exit(1); } bzero(&recvbuf , sizeof(recvbuf)); while( ( num = recvfrom(socketfd , &recvbuf , sizeof(recvbuf) , 0 , (struct sockaddr*)&server , &addrlen)) > 0){ 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(1); } } void ShutDown(){ sentbuf.command = SHUTDOWN; sendto(socketfd , &sentbuf , sizeof(sentbuf) , 0 , (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), 0 , (struct sockaddr*)&server , sizeof(server)); bcopy(sentbuf.buf , filename , sizeof(sentbuf.buf)); int fd ; fd = open(filename , O_RDONLY); if(fd < 0){ perror("The file is not exist!\n"); exit(1); } recvfrom(socketfd , &recvbuf , sizeof(recvbuf), 0 , (struct sockaddr*)&server , &addrlen); if( recvbuf.command == START ){ int no = 0 ; while( ( num = read(fd , sentbuf.buf , INFOLEN)) > 0 ){ sentbuf.no = no ; sentbuf.command = CONTENT; sentbuf.len = strlen(sentbuf.buf); sendto(socketfd , &sentbuf , sizeof(sentbuf) , 0 , (struct sockaddr*)&server,sizeof(server)); no++; bzero(&sentbuf , sizeof(sentbuf)); } bzero(&sentbuf , sizeof(sentbuf)); sentbuf.command = END; sendto(socketfd , &sentbuf , sizeof(sentbuf) , 0 , (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" /*-----------------------变量声明区------------------*/ int socketfd; int addrlen; struct sockaddr_in server; struct sockaddr_in client; struct protocol sentbuf; struct protocol recvbuf; int num; char ip[20]; int port; int choice; int main(){ /*-------------create UDP socket------------*/ if((socketfd = socket(AF_INET,SOCK_DGRAM,0)) == -1){ perror("socket error\n"); exit(1); } /*-----------------IO-----------------------*/ printf("Please input the ip:\n"); scanf("%s",ip); printf("Please input the port:\n"); scanf("%d",&port); /*-----------------bind----------------------*/ bzero(&server,sizeof(server)); server.sin_family = AF_INET; server.sin_port = htons(port); server.sin_addr.s_addr = inet_addr(ip); if (bind(socketfd,(struct sockaddr *)&server,sizeof(server)) == -1){ perror("bind error\n"); exit(1); } /*---------------------调试信息------------ addrlen = sizeof(client); recvfrom(socketfd,&recvbuf,sizeof(recvbuf),0,(struct sockaddr *)&client,&addrlen); num = strlen(recvbuf.buf); recvbuf.buf[num] = ‘\0‘; printf("command %d\n",recvbuf.command ); printf("len %d\n",recvbuf.len ); printf("no %d\n", recvbuf.no); printf("buf %s\n",recvbuf.buf ); */ addrlen = sizeof(client); while(1){ bzero(&recvbuf,sizeof(recvbuf)); num =recvfrom(socketfd,&recvbuf,sizeof(recvbuf),0,(struct sockaddr *)&client,&addrlen); choice = recvbuf.command; if(choice == DOWNLOAD){ char buf[100]; int fd; fd = open((recvbuf.buf),O_RDONLY); if(fd <0){ sentbuf.command = NO; sendto(socketfd,&sentbuf,sizeof(sentbuf),0,(struct sockaddr *)&client,sizeof(client)); printf("no such file!\n"); exit(1); } else{ sentbuf.command = YES; sendto(socketfd,&sentbuf,sizeof(sentbuf),0,(struct sockaddr *)&client,sizeof(client)); recvfrom(socketfd,&recvbuf,sizeof(recvbuf),0,(struct sockaddr *)&client,&addrlen); if(recvbuf.command == START){ int no =0; while((num = read(fd,sentbuf.buf,INFOLEN)) >0){ sentbuf.no = no; sentbuf.command = CONTENT; sentbuf.len = strlen(sentbuf.buf); sendto(socketfd,&sentbuf,sizeof(sentbuf),0,(struct sockaddr *)&client,sizeof(client)); no++; bzero(&sentbuf,sizeof(sentbuf)); } bzero(&sentbuf,sizeof(sentbuf)); sentbuf.command = END; sendto(socketfd,&sentbuf,sizeof(sentbuf),0,(struct sockaddr *)&client,sizeof(client)); } } } else if(choice == UPLOAD){ printf("The client want to upload the file: %s\n",recvbuf.buf); printf("Please choice start or no? \n"); printf("5 :start, 4: no\n"); scanf("%d",&sentbuf.command); sendto(socketfd,&sentbuf,sizeof(sentbuf),0,(struct sockaddr *)&client,sizeof(client)); if(sentbuf.command ==START){ int no =0; int fd =open(recvbuf.buf,O_CREAT | O_TRUNC |O_WRONLY,0644); if(fd < 0){ perror("create file error\n"); exit(1); } bzero(&recvbuf,sizeof(recvbuf)); while((num = recvfrom(socketfd,&recvbuf,sizeof(recvbuf),0,(struct sockaddr *)&server,&addrlen)) >0){ if(recvbuf.command == CONTENT){ if(no == recvbuf.no){ write(fd,recvbuf.buf,recvbuf.len); printf("kkk%s\n",recvbuf.buf ); bzero(&recvbuf,sizeof(recvbuf)); } else{ perror("The file no is not same.Some message is missed! error occured! \n"); break; } } if(recvbuf.command == END){ close(fd); printf("transmission is successful!\n"); break; } } } else if(sentbuf.command == NO){ printf("Not to trans the file\n"); } else{ perror("error! wrong choice!\n"); exit(1); } } else if (recvbuf.command == SHUTDOWN){ printf("Now the server is shutdown!\n"); break; } } /*----------------------close ----------*/ close(socketfd); return 0; }
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
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原文地址：http://www.cnblogs.com/turnips/p/4915782.html
