1.项目描述

基于Soket聊天服务器，实现服务器和客户端的文件传输。

Linux系统下建立Socket聊天服务器_趣知boy的博客-CSDN博客

ls   获取服务器文件列表   
pwd  获取服务器当前路径
cd   对服务器目录的操作  +dir
quit 退出连接  put 上传文件到服务器  +file_name
get 获取服务器数据    +file_namelcd 对客户端目录的操作 +dir
lls 列出客户端所有文件 dofile 创建文件

项目结构

2.函数准备

2.1 gets函数

gets 从标准输入流（通常是键盘）读取一行字符串，并将其存储在指定的字符数组中。

其比较重要的一个功能是阻塞

   printf("请输入您的姓名：");gets(name);printf("您的姓名是：%s\n", name);

2.2 popen函数、fread函数

size_t fread(void *ptr, size_t size, size_t count, FILE *stream);

该函数可以读取指定数量（count = 1）的元素，每个元素的大小为size个字节，从指定文件（stream）中读取到内存指针（ptr）所指的位置。

2.3 access 函数

用于判断文件或目录是否具有某种权限。

int access(const char *pathname, int mode);

F_OK：检查文件是否存在
R_OK：检查读权限是否存在
W_OK：检查写权限是否存在
X_OK：检查执行权限是否存在

返回值：

如果路径名指定的文件或目录具有所需的权限，则返回0。
如果权限不足，则返回-1，并且errno设置为适当的错误码

2.4 exit 函数

exit函数是一个用于终止程序运行的函数。当调用exit函数时，程序将立即退出并返回到操作系统。

2.5 strtok 函数

char *strtok(char *str, const char *delim);

其中str是要进行分割的字符串，delim是作为分隔符的字符串。函数返回一个指向被分割出的子字符串的指针。

strtok函数陷阱：会改变指针指向的字符串，所以想保留原来str需要用strcpy复制出来处理。

token = strtok(str, ",");
while (token != NULL) {printf("%s\n", token);token = strtok(NULL, ",");
}return 0;

执行上述代码会输出以下结果：

Hello

World

This

Strtok

2.6 chdir函数

更改当前工作目录

int chdir(const char *path);

参数：Path 目标目录，可以是绝对目录或相对目录。

返回值：成功返回0 ，失败返回-1

3.项目代码

3.1服务器代码

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <ctype.h>
#include <arpa/inet.h>
#include "config.h" 
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>struct Msg msg;
int ss_fd;void handler_cmd(char *cmd){int cmd_int,fd;char *p;FILE *file;char *cmd_pre=cmd;//handle the cmd to numberif(!strcmp(cmd_pre,"ls")) cmd_int=ls;if(!strcmp(cmd_pre,"pwd")) cmd_int=pwd;  if(!strcmp(cmd_pre,"quit")) cmd_int=quit;if(!strcmp(cmd,"lls"))      cmd_int=lls;if(strstr(cmd,"lcd")!=NULL) cmd_int=lcd;if(strstr(cmd_pre,"cd")!=NULL) cmd_int=cd;if(strstr(cmd_pre,"put")!=NULL) cmd_int=put;if(strstr(cmd_pre,"get")!=NULL) cmd_int=get;//handle cmd switch(cmd_int){case ls:case pwd:file=popen(cmd,"r");fread(msg.data,sizeof(msg.data),1,file);printf("%s",msg.data);write(ss_fd,&msg,sizeof(msg));break;case cd:p=strtok(cmd," ");p=strtok(NULL," ");printf("dir:%s \r\n",p);strcpy(msg.data,"change dir over \r\n");write(ss_fd,&msg,sizeof(msg));   //must give a msg backchdir(p);break;case get:p=strtok(cmd," ");p=strtok(NULL," ");printf("dir:%s \r\n",p);	if(!access(p,F_OK)){  //if have this filemsg.flag=dofile;fd=open(p,O_RDONLY);read(fd,&msg.data,sizeof(msg.data));send(ss_fd,&msg,sizeof(msg),0);close(fd);}else{   //if no this filesend(ss_fd,"no this file \r\n",16,0);}break;case put:p=strtok(cmd," ");p=strtok(NULL," ");printf("dir:%s \r\n",p);fd=open(p,O_RDWR|O_CREAT,0666);write(fd,&msg.data,strlen(msg.data));close(fd);strcpy(msg.data,"i have got a file.\r\n");write(ss_fd,&msg,sizeof(msg));   //must give a msg backbreak;case quit:msg.flag=quit;printf("quit==========\r\n");exit(-1);}}int main(void)
{int s_fd,nread,len;struct sockaddr_in s_ddr;  //build server msgstruct sockaddr_in c_ddr;  //save clinet msgs_fd= socket(AF_INET, SOCK_STREAM, 0);//1.build a soket specifiedif(s_fd==-1){perror("error is");}//2.build all binds_ddr.sin_family=AF_INET;s_ddr.sin_port=htons(8880);s_ddr.sin_addr.s_addr=htonl(INADDR_ANY);//give the bindbind(s_fd,(struct sockaddr *)&s_ddr,sizeof(s_ddr));//3.waite for clientlisten(s_fd,8);//4.accept come and connect for oncelen=sizeof(c_ddr);while(1){ss_fd=accept(s_fd,(struct sockaddr *)&c_ddr,&len);if(ss_fd == -1){perror("accept:");}printf("conect succese!==========\r\n");//5.read from connect ss_fdif(fork()==0){   //creat kid pid for handler msg and cmd //5.2 read	while(1){memset(&msg,'\0',sizeof(msg));   //clear msgprintf("====================\r\n");nread=read(ss_fd,&msg,sizeof(msg));if(nread==0){                 // cannot recv cmd printf("connect is cutdon! \r\n");break;}else{                        //can recive cmd printf("server  receved  cmd:%s \r\n",msg.cmd); printf("====================\r\n");handler_cmd(msg.cmd);    //hander the cmd  give msg data		}}}}close(ss_fd);close(s_fd);return 0;
}

3.2客户端代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include "config.h" 
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>int cmd_to_number(char *cmd)
{if(!strcmp(cmd,"ls")) return ls;if(!strcmp(cmd,"pwd")) return pwd;  if(!strcmp(cmd,"quit")) return quit;if(!strcmp(cmd,"lls")) return lls;if(strstr(cmd,"lcd")!=NULL) return lcd;if(strstr(cmd,"cd")!=NULL) return cd;if(strstr(cmd,"put")!=NULL) return put;if(strstr(cmd,"get")!=NULL) return get;return -1;}int handler_cmd(struct Msg msg, int s_fd)
{//handle cmd int fd,n_read; char p_pre[12];char *p=NULL;int ret=cmd_to_number(msg.cmd);switch(ret){case ls:case pwd:case cd:send(s_fd,&msg,sizeof(msg),0);break;case get:send(s_fd,&msg,sizeof(msg),0);break;case put:strcpy(p_pre,msg.cmd);printf("dir:%s \r\n",p_pre);p=strtok(p_pre," ");p=strtok(NULL," ");   //get file_name	printf("dir:%s \r\n",p);if(!access(p,F_OK)){  //if have this filefd=open(p,O_RDONLY);n_read=read(fd,&msg.data,1024);if(n_read>=1024){printf("file over 1024! faild! \r\n");} send(s_fd,&msg,sizeof(msg),0);memset(&msg.data,0,1024);printf("client put cmd is: %s \r\n",msg.cmd);close(fd);}else{   //if no this filesend(s_fd,"no this file",16,0);}break;			case lls:system("ls");break;case lcd:strcpy(p_pre,msg.cmd);p=strtok(p_pre," ");p=strtok(NULL," ");   //get file_printf("dir:%s \r\n",p);chdir(p);break;case quit:send(s_fd,&msg,sizeof(msg),0);close(s_fd); exit(-1);}return ret;
}  void handle_server_msg(struct Msg msg,int s_fd)
{int n_read,fd;char *p;struct Msg recv_msg; //this is new msg   use it becase need pre msg cmdn_read=read(s_fd,&recv_msg,sizeof(recv_msg));  //while blockif(n_read==0){printf("\r\n server is outline! ");exit(-1);}if(recv_msg.flag == dofile){p=strtok(msg.cmd," ");p=strtok(NULL," ");   //get file_name	fd=open(p,O_RDWR|O_CREAT,0666);printf("creat the file\r\n");write(fd,&recv_msg.data,strlen(recv_msg.data));close(fd);putchar('>');fflush(stdout);}else{           //normal direct cmdprintf("-------------------->\r\n");printf("%s >",recv_msg.data);printf("--------------------");putchar('>');fflush(stdout);}}int main(int argc,char *argv[])
{int flag,s_fd,n_read,ret;struct sockaddr_in c_ddr;struct Msg msg;//1.build sockets_fd=socket(AF_INET,SOCK_STREAM,0);//2.0 prepare server addrmemset(&c_ddr,0,sizeof(c_ddr)); //clear c_ddrc_ddr.sin_family=AF_INET;c_ddr.sin_port=htons(8880);inet_aton("127.0.0.1",&c_ddr.sin_addr);//2.connect server get s_fdif(connect(s_fd,(struct sockaddr *)&c_ddr,sizeof(c_ddr))==-1){perror("error");exit(-1);}printf("connect success==============\r\n");while(1){//1.get cmd form keyborad    and  handle cmd to servermemset(&msg,0,sizeof(msg));printf("\r\n >");gets(msg.cmd);int ret=handler_cmd(msg,s_fd);//2.handle the msg form serverif(ret==-1){printf("no this cmd!\r\n ");fflush(stdout);continue;}if(ret==5 || ret==6){printf("client cmd!\r\n ");fflush(stdout);continue;}	handle_server_msg(msg,s_fd);}close(s_fd);return 0;
}

4.问题总结

在put 发送文件中，当文件大小超过给定字节就会溢出，导致整个结构体崩坏，破坏cmd。
思考：除了加大给定字节大小，还有其它办法吗？strcpy是怎么实现的
read函数陷阱：read函数读的字节小于fd文件字节，会崩坏buf里的数据。
strtok函数会破坏使用的字符串，要保留原来字符串需要strcpy复制出来处理。
本地命令不用服务器处理的命令，ret=5，ret=6不要进入hanle_server_msg用recv函数阻塞