Telnet模拟系统（Linux c）

第3章详细设计和实现

3.1相关技术

  　　1）tcp编程，主要包括socket()函数、bind()函数、listen()函数、recv()函数、send()函数以及客户端的connect()函数。

　　2）c语言中对结构体的操作，和对字符串的比较

　　3）对文件的读写操作

　　4）popen调用shell

 

3.2开发工具和运行环境

  　　本系统在ubantu 16.4 lts环境下开发，所用的工具为vi编辑器和gedit编辑器，以及gcc编译工具。

 

 

3.3主要功能的源码

3.3.1服务器端socket的建立

    if ( (sockfd = socket(af_inet, sock_stream, 0)) < 0 )  //创建socket

        printf( "socket failed" );

 

    /* 设置端口快速重用*/

    optval = 1;

    if ( setsockopt(sockfd, sol_socket, so_reuseaddr, (void *)&optval, sizeof(int)) < 0 )

        printf( "setsockopt failed" );

 

    server_addr.sin_family = af_inet;

    server_addr.sin_port = htons( port );

    server_addr.sin_addr.s_addr = htonl( inaddr_any );

 

   if ( bind(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in)) < 0 ) //绑定ip和端口号

        printf( "bind failed" );

 

    if ( listen(sockfd, max_listen) < 0 ) //建立监听

        printf( "listen failed" );

 

3.3.2对客户端的发送信息进行处理

while ( 1 ) {

    if ( (connfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_size)) < 0 ) //响应客户端请求

            printf( "accept failed" );

        printf( "server accept a client: ip = %s\n",inet_ntoa(client_addr.sin_addr) ); //打印客户端ip

        

        /* 创建子进程处理客户端请求 */

        if ( (pid = fork()) == 0 ) {

            while ( 1 ) {

                /* 接受客户端信息 */

                if ( (recv_bits = recv(connfd, buffer, buf_size, 0)) < 0 )

                    printf( "recv failed" );

 

                /* 去除最后一个字符 */

                buffer[recv_bits - 1] = '\0';

 

                /* 用户名鉴定 */

                if ( recv_type == username ) {

                    if ( strcmp(name, buffer) != 0 ) {

                  if ( send(connfd, error_user,strlen(error_user), 0) < 0 )

                            printf( "send failed" );

break;

                    }else{

if ( send(connfd, correct_user,strlen(correct_user), 0) < 0 )

                            printf( "send failed" );

}

printf("%s正在登录：",buffer);

                        recv_type = password;  //设置标志为密码鉴定模式

                }

                /* 密码鉴定 */

                else if ( recv_type == password ) {

                    if ( strcmp(passwd, buffer) != 0 ) { //验证密码

                  if ( send(connfd, error_password,strlen(error_password), 0) < 0 )

                            printf( "send failed" );

                    } else {

                    if ( send(connfd, success_login, strlen(success_login), 0) < 0 )

                            printf( "send failed" );

printf("用户登录成功！\n");

recv_type = command;  //设置标志为命令模式

                    }                

                }

/* 命令模式 */

else if( recv_type == command ) {

command(connfd,buffer);   

puts("客户端输入的命令为：");

puts(buffer);                 

                }

            }

            close( sockfd );

            close( connfd );

            exit ( 0 );

        }

        else

            close( connfd );

}

 3.3.3 执行命令函数

int command(int connfd,char*command)

{    

    /*

     *  作用：通过popen调用shell执行command命令

     *  connfd: 客户端标识

     *  command: 命令字符串

    */

    file *fstream = null;      

    char buff[1024];    

    memset(buff, 0, sizeof(buff));   

if ( strcmp(exit_command, command) == 0 ) { //退出

        if ( send(connfd, exit_command,strlen(exit_command), 0) < 0 )

          printf( "send failed" );

printf("客户端已断开连接！\n");

  return 0;

    }

    if(null == (fstream = popen(command,"r")))      

    {     

        fprintf(stderr,"execute command failed: %s",strerror(errno));      

        return -1;      

    }   

 

    while(null != fgets(buff, sizeof(buff), fstream))

    {  

        //printf("%s",buff);  

if ( send(connfd, buff,strlen(buff), 0) < 0 ) //将命令执行结果发送至客户端

         printf( "send failed" );    

    }

    pclose(fstream);    

 

    return 0;     

}

3.3.4客户端发送与接受信息

int send_recv( int connfd,char flag )

{

 /*

     *  作用：客户端与服务器端信息的处理

     *  connfd: 服务器端标识

 *  flag: 输入类比标识

    */

    char input_buf[ buf_size ]; //定义字符串存放输入信息

    char recv_buf[ buf_size ]; //定义字符串存放服务器端返回信息

memset(input_buf, 0, sizeof(input_buf));

memset(recv_buf, 0, sizeof(recv_buf));

    

fgets( input_buf, buf_size, stdin ); //获取用户输入

    input_buf[strlen(input_buf) - 1] = '\0'; //去除最后一个输入的确认

 

    /* 向服务器发送消息 */

    if ( send(connfd, input_buf, buf_size, 0) < 0 )

        printf( "send failed" );

 

    /* 从服务器接受消息 */

    if ( recv(connfd, recv_buf, buf_size, 0) < 0 )

        printf( "recv failed" );

 

/* 用户名处理 */

    if ( flag == 'u' ) {

        if ( strcmp(recv_buf, error_user) == 0 ) {  //用户名错误

            puts( error_user );

            return false;

        }

    }

/* 密码处理 */

    else if ( flag == 'p' ) {

        if ( strcmp(recv_buf, error_password) == 0 )

          {  puts( error_password );  //密码错误

 return false;

}

    }

/* 命令处理 */

else if( flag == 'c' )

{

if ( strcmp(recv_buf, exit_command) == 0 ) {  //退出

printf("连接已断开\n");          

return false;

     }

puts(recv_buf); //命令结果输出

}

    return true;

}

 

第7章 附录

7.1服务器端

 

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <netinet/in.h>

 

#define port         3333

//用户名和密码

char *name="twain";

char *passwd="123";

 

#define max_listen    10

#define buf_size     1024

#define username   0

#define password   1   

#define command    2

 

//登录过程状态标识

char *error_user = "error user name";

char *error_password = "error password";

char *correct_user = "correct user";

char *success_login = "correct password";

char *exit_command = "exit";

char *exit_tip="退出连接！";

 

 

/*

* 介绍：服务器端

* 功能：

*    1.接受客户端的登录请求并验证

*    2.接受客户端的命令在本地执行并返回执行结果

*/

 

int command(int connfd,char*command)

{    

    /*

     *  作用：执行command命令

     *  connfd: 客户端标识

     *  command: 命令字符串

    */

    file *fstream = null;      

    char buff[1024];    

    memset(buff, 0, sizeof(buff));   

if ( strcmp(exit_command, command) == 0 ) { //退出

        if ( send(connfd, exit_command,strlen(exit_command), 0) < 0 )

          printf( "send failed" );

printf("客户端已断开连接！\n");

  return 0;

    }

    if(null == (fstream = popen(command,"r")))      

    {     

        fprintf(stderr,"execute command failed: %s",strerror(errno));      

        return -1;      

    }   

 

    while(null != fgets(buff, sizeof(buff), fstream))

    {  

        //printf("%s",buff);  

if ( send(connfd, buff,strlen(buff), 0) < 0 ) //将命令执行结果发送至客户端

            printf( "send failed" );    

    }/*

if(null != fgets(buff, sizeof(buff), fstream))

    {  

        //printf("%s",buff);  

if ( send(connfd, buff,strlen(buff), 0) < 0 )

            printf( "send failed" );    

    }else{

if ( send(connfd, "..",sizeof("buff"), 0) < 0 )

            printf( "send failed" );

}*/

    pclose(fstream);    

 

    return 0;     

}

 

 

int main( int argc, char *argv[] )

{

    int    sockfd, connfd;

    int optval;

    int recv_type = username;  //默认为username，即用户名输入模式

    int client_size;

    int recv_bits;  

    char buffer[ buf_size ];

 

    pid_t pid;

    struct sockaddr_in client_addr, server_addr;

 

    client_size = sizeof( struct sockaddr_in );

    /* 初始化各变量为零 */

    memset( buffer, 0, buf_size );

    memset( &server_addr, 0, sizeof(server_addr) );

    memset( &client_addr, 0, sizeof(server_addr) );

 

    if ( (sockfd = socket(af_inet, sock_stream, 0)) < 0 )  //创建socket

        printf( "socket failed" );

 

    /* 设置端口快速重用*/

    optval = 1;

    if ( setsockopt(sockfd, sol_socket, so_reuseaddr, (void *)&optval, sizeof(int)) < 0 )

        printf( "setsockopt failed" );

 

    server_addr.sin_family = af_inet;

    server_addr.sin_port = htons( port );

    server_addr.sin_addr.s_addr = htonl( inaddr_any );

 

   if ( bind(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr_in)) < 0 ) //绑定ip和端口号

        printf( "bind failed" );

 

    if ( listen(sockfd, max_listen) < 0 ) //建立监听

        printf( "listen failed" );

 

printf("telnet服务器已开启……\n");

    while ( 1 ) {

    if ( (connfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_size)) < 0 ) //响应客户端请求

            printf( "accept failed" );

        printf( "server accept a client: ip = %s\n",inet_ntoa(client_addr.sin_addr) ); //打印客户端ip

        

        /* 创建子进程处理客户端请求 */

        if ( (pid = fork()) == 0 ) {

            while ( 1 ) {

                /* 接受客户端信息 */

                if ( (recv_bits = recv(connfd, buffer, buf_size, 0)) < 0 )

                    printf( "recv failed" );

 

                /* 去除最后一个字符 */

                buffer[recv_bits - 1] = '\0';

 

                /* 用户名鉴定 */

                if ( recv_type == username ) {

                    if ( strcmp(name, buffer) != 0 ) {

                     if ( send(connfd, error_user,strlen(error_user), 0) < 0 )

                            printf( "send failed" );

break;

                    }else{

if ( send(connfd, correct_user,strlen(correct_user), 0) < 0 )

                            printf( "send failed" );

}

printf("%s正在登录：",buffer);

                        recv_type = password;  //设置标志为密码鉴定模式

                }

                /* 密码鉴定 */

                else if ( recv_type == password ) {

                    if ( strcmp(passwd, buffer) != 0 ) { //验证密码

                     if ( send(connfd, error_password,strlen(error_password), 0) < 0 )

                            printf( "send failed" );

                    } else {

                       if ( send(connfd, success_login, strlen(success_login), 0) < 0 )

                            printf( "send failed" );

printf("用户登录成功！\n");

recv_type = command;  //设置标志为命令模式

                    }                

                }

/* 命令模式 */

else if( recv_type == command ) {

command(connfd,buffer);   

puts("客户端输入的命令为：");

puts(buffer);                 

                }

            }

            close( sockfd );

            close( connfd );

            exit ( 0 );

        }

        else

            close( connfd );

    }

    return 0;

}

 

 

7.2客户端

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <assert.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <netinet/in.h>

 

 

#define true        1

#define false       -1

#define buf_size     1024

 

//登录过程状态标识

char *error_user = "error user name";

char *error_password = "error password";

char *correct_user = "correct user";

char *success_login = "correct password";

char *exit_command = "exit";

char *exit_tip="退出连接！";

 

/*

* 介绍：客户端

* 功能：

*    1.登录服务器端

*    2.登录后在服务器端对文件进行操作

*/

 

 

int send_recv( int connfd,char flag )

{

 /*

     *  作用：客户端与服务器端信息的处理

     *  connfd: 服务器端标识

 *  flag: 输入类比标识

    */

    char input_buf[ buf_size ]; //定义字符串存放输入信息

    char recv_buf[ buf_size ]; //定义字符串存放服务器端返回信息

memset(input_buf, 0, sizeof(input_buf));

memset(recv_buf, 0, sizeof(recv_buf));

    

fgets( input_buf, buf_size, stdin ); //获取用户输入

    input_buf[strlen(input_buf) - 1] = '\0'; //去除最后一个输入的确认

 

    /* 向服务器发送消息 */

    if ( send(connfd, input_buf, buf_size, 0) < 0 )

        printf( "send failed" );

 

    /* 从服务器接受消息 */

    if ( recv(connfd, recv_buf, buf_size, 0) < 0 )

        printf( "recv failed" );

 

/* 用户名处理 */

    if ( flag == 'u' ) {

        if ( strcmp(recv_buf, error_user) == 0 ) {  //用户名错误

            puts( error_user );

            return false;

        }

    }

/* 密码处理 */

    else if ( flag == 'p' ) {

        if ( strcmp(recv_buf, error_password) == 0 )

          {  puts( error_password );  //密码错误

 return false;

}

    }

/* 命令处理 */

else if( flag == 'c' )

{

if ( strcmp(recv_buf, exit_command) == 0 ) {  //退出

printf("连接已断开\n");          

return false;

        }

puts(recv_buf); //命令结果输出

}

    return true;

}

 

 

int main( int argc, char *argv[] )

{

    int    connfd;

    int serv_port;

    char recv_buf[ buf_size ];

    struct sockaddr_in    serv_addr;

 

    if ( argc != 3 ) {

        printf( "输入格式为: ./c  [ip] [port]\n" );

        exit ( 1 );

    }

 

    memset( &serv_addr, 0, sizeof(struct sockaddr_in) );//置零

 

    serv_addr.sin_family = af_inet;

    serv_addr.sin_port = htons( atoi(argv[2]) );

    inet_aton( argv[1], &serv_addr.sin_addr );

 

    if ( serv_addr.sin_port == 0 ||serv_addr.sin_addr.s_addr == 0 ) {

        fprintf( stderr, "输入格式为: ./c  [ip] [port]\n" );

        exit ( 1 );

    }

 

    connfd = socket( af_inet, sock_stream, 0 );  //创建socket

    if ( connfd < 0 )

        printf( "socket failed" );

 

    if ( connect(connfd, (struct sockaddr *)&serv_addr,sizeof(struct sockaddr)) < 0 ) //连接服务器

    {    

        printf( "connect failed" );

    exit(0);

    }

printf("请输入用户名：");

/*输入操作*/

    if ( send_recv( connfd, 'u' ) == true )

{

   printf("请输入密码：");

       if ( send_recv( connfd,'p' )== true )

{

while(1)

{

printf("guest@ubantu:");

if ( send_recv( connfd, 'c' )== false )

{

    close( connfd );

        exit(0);

}

}

}

}

    close( connfd );

    return 0;

}