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" /*-----------------------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[];
int port;
int choice; int main(){ /*-------------create UDP socket------------*/
if((socketfd = socket(AF_INET,SOCK_DGRAM,)) == -){
perror("socket error\n");
exit();
} /*-----------------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)) == -){
perror("bind error\n");
exit();
} /*---------------------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(){
bzero(&recvbuf,sizeof(recvbuf));
num =recvfrom(socketfd,&recvbuf,sizeof(recvbuf),,(struct sockaddr *)&client,&addrlen);
choice = recvbuf.command;
if(choice == DOWNLOAD){
char buf[];
int fd;
fd = open((recvbuf.buf),O_RDONLY);
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;
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));
}
}
}
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),,(struct sockaddr *)&client,sizeof(client));
if(sentbuf.command ==START){
int no =;
int fd =open(recvbuf.buf,O_CREAT | O_TRUNC |O_WRONLY,);
if(fd < ){
perror("create file error\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);
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();
} }
else if (recvbuf.command == SHUTDOWN){
printf("Now the server is shutdown!\n");
break;
}
} /*----------------------close ----------*/
close(socketfd);
return ;
}
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