NAME

Telnet Server – telnetd

SYNOPSIS

#include <posh_init.h>
#include < sys.h >

pthread_create(&pid, &attr, &telnet_shell, 0);

THREAD telnetd(int(*shell)(void));

// For dual TCP stack:

THREAD telnetd(int(*shell)(void), int ip_ver);

DESCRIPTION

The telnet server provides a network telnet protocol and utilizes the vtty server technology and the posh shell server for user interaction via telnet. Typically, when initialized, it allows users to query files, examine the file structure, create new files and look at the content of files, all over the network. It is a minimal implementation for memory reasons. It does not support terminal formating of any kind and only supports the absolute minimal set of commands.

The telnet server inputs characters and outputs results of command requests via the network. The first character data negotiates the telnet protocol. The first command request is a login request. Unlike many implementations, the login support is contained within posh – it does not have a separate thread for this purpose. The .login file is specified at posh creation time in the initialization structure.

The posh_init initialization structure also specifies the mount points for two file systems. These mount points are important to avoid attempts to list non-existent files. Setup these mount points at creation time for proper operation. The final elements of the initalization structure are the input and output streams. These two are specified as files. The structure is shown below.

SPECIFIC OPTIONS

Dual stack options:

EXAMPLE

Posh initialization structure.

struct set_posh
{
    char *stdinstring;          // set the input stream
    char *stdoutstring;         // set output stream
    char *mountpoint;           // set first file mount point
    char *mountpoint2;          // set second file mount point
    char *loginfile;
};

This partial example shows the creation and registration of the telnetd server and its associated vtty file I/O. After creation, posh is created which interacts via the vtty file I/O ports for input and output.

int start_posh(void);

THREAD telnet_shell(void *arg)
{
        telnetd(start_posh);
}

Telnet start for dual TCP stack:

THREAD telnet_shell(void *arg)
{
	telnetd(start_posh, TELNETD_IP_VER);
	return 0; //just to avoid warning	
}

...

int start_posh(void)
{
        struct set_posh *set_posh_tty;
        pthread_t poshTid;
        pthread_attr_t poshattr;
        struct sched_param poshPriority;


        if( (set_posh_tty = malloc(sizeof(struct set_posh)))==NULL)
        {
            xprintf("posh create - no memory\n");
            return 0;
        }
        set_posh_tty->stdinstring = "/dev/vtty";
        set_posh_tty->stdoutstring = "/dev/vtty";
        set_posh_tty->mountpoint = "/dev/rd/d1";
        set_posh_tty->mountpoint2 = NULL;
        set_posh_tty->loginfile = "/dev/rd/d1/.login";

        pthread_attr_init(&poshattr);
        pthread_attr_setstacksize(&poshattr, 1400);
        poshPriority.sched_priority = 5;
        pthread_attr_setdetachstate(&poshattr, PTHREAD_CREATE_DETACHED);
        pthread_attr_setschedparam(&poshattr, &poshPriority);

        pthread_create(&poshTid, &poshattr, (void *(*)(void*))posh, set_posh_tty);

        pthread_attr_destroy(&poshattr);
        return 1;
}

/*
 * Start telnetd example
 */
  ...
        pthread_attr_init(&attr);
        myNewPriority.sched_priority = 6;
        pthread_attr_setschedparam(&attr, &myNewPriority);
        pthread_attr_setstacksize(&attr, 1024);

        if(pthread_create(&pid, &attr, &telnet_shell, 0)!=0)
        {
                xprintf("pthread_create = %d\n", errno);
                pthread_exit(0);
        }
        pthread_attr_destroy(&attr);

        if(dir_register("/dev/vtty", pid, TYPE_SERVER)==0)
        {
                xprintf("dir_register = %d\n", errno);
                pthread_exit(0);
        }
        xprintf("\ntelnetd started!\n");

  ...

TELNET – POSH COMMANDS AND OPTIONS

• help – help listing
• alias [alias_name=”value”] – setup an alias for an expression
• cat – concatenate output
• cd <dir> – change directory to <dir>
• chmod <mode> <dir | file> – change a file’s access control mode

  mode – file access mode, for example “rwx”

  dir | file – path to the target file to which mode is setting

• cp <src> <dst> – copy a file from <src> path to <dst> path
• exit – exit the posh shell
• ln <src> <dst> – create link to file

  src – target path for link

  dst – link name (with path)

• logout – logout of posh
• ls [option] – list directory contents

  -l – for long list

  -d – lists directories, not content

• mkdir <dir> – make a directory specified by <dir>
• mv <src> <dst> – move a file from <src> path to <dst> path
• printenv [env_name] – print all or part of environment

  printenv [VARIABLE] or printenv OPTION

  If VARIABLE or OPTION not specified, then all present will be printed

• pwd – present working directory
• rm <file> – remove a file
• rmdir – remove a directory
• setenv [env_name=”value”] – set an environment variable

  Example: setenv PATH “/d0:/sd/d1:/sd/d1/d2”

• unalias <alias_name> – delete an alias
• useradd <username> <password> – add a user with a password
• userdel <username> – delete a user
• userpasswd <username> <oldpassword> <newpassword> – set (or reset) a user password

NOTES

There is a demo available for the Unison and DSPnano telnetd server which is found in installdir/demos.

SEE ALSO

posh, login