====== VModem ======
The script that simulates a Hayes compatible modem.

A copy of vmodem can be also found at Github, at https://github.com/molivil/vmodem

===== vmodem.sh =====
The main script. This script will simulate a modem by answering to standard Hayes commands. 
It will open the serial port for communication and execute the dialed number as a linux shell script, however you could probably use any execututable with minor modification.
For example, if you issue the command ATD12345, the script will look for a file 12345.sh in 
the working directory and execute it and output contents to console.

This script can be run standalone, or with the accompanying T1.sh and ppp.sh scripts, which will
enable point-to-point serial to ethernet connections. 

<code bash vmodem.sh>
#!/bin/bash
#
# --------------------------------
# VMODEM - Virtual Modem bootstrap
# --------------------------------
# Oliver Molini 2020-2022
#
# Additional credits:
# - Billy Stoughton II for bug fixes and contributions
# - Hamish for helping test Windows 2000 compatibility
#
# Licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License
# https://creativecommons.org/licenses/by-nc-sa/4.0/

# Tested working out of box with the following client configurations:
#
# o Standard VT100 terminal
# o HyperTerminal
# o PuTTY
#
# PPP dial-up connectivity tested to initialize under the following configurations:
#
# o Windows 3.1
#   - Trumpet Winsock 3.0 revision D
#
# o Windows 95 OSR 2.5 + DUN 1.4
#   - Generic Modem
#     - Standard 28800 bps Modem
#
# o Windows 98
#   - Generic Modem
#     - Standard 9 600 bps modem
#     - Standard 33 600 bps modem
#     - Standard 56 000 bps V90 modem
#     - Standard 56 000 bps X2 modem
#     - Standard 56 000 bps K56Flex modem
#
# o Windows 2000
#   - Generic Modem
#     - Standard 19200 bps Modem
#
# Help us test and add more supported systems! 
# Contact us on Discord, links at the bottom of the Virtual Modem page.
#

# Script version
vmodver=1.7.1

# CONFIGURATION
# -----------------------
# Variable: serport
# serport specifies which local serial device to use.
# For example, "ttyUSB0" will tell the script to use
# to use /dev/ttyUSB0 for communication.
# Common values: ttyUSB0 or ttyAMA0
#
serport=ttyUSB0

# Variable: baud
# baud will tell the script to open the serial port at
# specified symbol rate. When connecting, make sure
# your client computer uses the same baud than what
# has been specified here.
# Common baud rates: 9600, 19200, 38400, 57600
#
# Default:
# baud=57600
#
#baud=9600
#baud=38400
baud=57600

# Variable: etherp
# Sets the name of the ethernet device for PPP connections.
# 
# eth0 for wired 
# wlan0 for wireless
#
etherp=eth0

# Variable: echoser
# echoser sets the default behaviour of echoing serial
# data back to the client terminal. The default is 1.
#
echoser=1

# Variable: resultverbose
# Controls default behavior when printing Hayes result
# codes. 
# When 0, prints result codes in numerical form. (eg. 0)
# When 1, prints result codes in english. (eg. CONNECT)
# Default is 1.
resultverbose=1

# Variable: TERM
# Tells the script and environment which type of terminal to emulate.
# It is only useful to change this, if you're using a serial 
# terminal to connect to this script. If you're connecting form a ANSI 
# cabable machine such as DOS, you may want to use TERM="ansi"
#
TERM="vt100"

# EXPORT SHELL VARS
# -----------------
export serport
export baud
export etherp
export TERM

# FUNCTIONS
# ---------
#

#INITIALIZE SERIAL SETTINGS
ttyinit () {
  stty -F /dev/$serport $baud
  stty -F /dev/$serport sane
  stty -F /dev/$serport raw
  stty -F /dev/$serport -echo -icrnl onlcr opost clocal -crtscts
}

# SEND MESSAGE ON SCREEN AND OVER SERIAL
sendtty () {
  # Prints message in console and over serial. Message is given as first parameter.
  message="$1"
  echo -en "$message" | tee /dev/$serport
}

readtty () {
  # Reads input from TTY and stores it in variable given as first parameter
  line=
  while [[ -z "$line" ]]; do
    charhex=`head -c 1 /dev/$serport | xxd -p -`
    char="`echo -e "\x$charhex"`"
    echo -n "$char"
    echo -n "$char" > /dev/$serport
    # Newline received
    if [ "$charhex" = "0d" -o "$charhex" = "0a" ]; then
      line=$buffer
      buffer=
      char=
      sendtty "\n"
    fi
    buffer=$buffer$char
  done
  local __resultvar=$1
  local result="$line"
  eval $__resultvar="'$result'"
}

export -f sendtty
export -f readtty
export -f ttyinit

# Open serial port for use. Allocate file descriptor
# and treat the serial port as a file.
ttyinit
exec 99<>/dev/$serport

sendtty "\n"
sendtty "Virtual Modem bootstrap for PPP link v$vmodver\n"
sendtty "Connection speed set to $baud baud.\n"
sendtty "My current IP address is $(hostname -I).\n"
sendtty "\n"
sendtty "TYPE \"HELP\" FOR COMMAND REFERENCE.\n"
sendtty "READY.\n"

# execute hayes commands
dohayes () {
  # default to error result code, if command not recognized
  result=4

  # Debugging
  #sendtty "COMMAND: $hcmd $hparm\n"

  # ATA
  # - A Answer
  if [[ $hcmd == 'A' ]]; then result=0; fi

  # ATD Dial a number
  if [[ $hcmd == 'D' ]]; then
    if [[ ! -z "$hparm" ]]; then
      number=$(echo $hparm |tr -dc '0-9')
      result=0
    fi
  fi

  # ATE Command echo to host
  # - E0 Commands are not echoed
  # - E1 Commands are echoed
  if [[ $hcmd == 'E' ]]; then
    if [[ $hparm == '' ]]; then echoser=0; result=0; fi
    if [[ $hparm == '0' ]]; then echoser=0; result=0; fi
    if [[ $hparm == '1' ]]; then echoser=1; result=0; fi
  fi

  # ATH Hang up or pick-up.
  # - H0 Go on-hook (Hang up)
  # - H1 Go off-hook
  if [[ $hcmd == 'H' ]]; then result=0; fi

  # ATM Speaker control
  # - M0 Speaker always off
  # - M1 Speaker on until carrier detected
  # - M2 Speaker always on
  # - M3 Speaker on only while answering
  if [[ $hcmd == 'M' ]]; then
    if [[ $hparm == '' ]]; then result=0; fi
    if [[ $hparm == '1' ]]; then result=0; fi
    if [[ $hparm == '2' ]]; then result=0; fi
    if [[ $hparm == '3' ]]; then result=0; fi
  fi

  # ATQn Result codes
  # Q0 Modem returns result codes
  # Q1 Quiet mode. Modem gives no result codes.
  if [[ $hcmd == 'Q' ]]; then
    if [[ $hparm == '' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '0' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '1' ]]; then resultverbose=2; result=0; fi
  fi

  # S Registers (just auto-accept)
  if [[ $hcmd == 'S' ]]; then
    result=0;
  fi

  # ATV Result codes in numerical or verbose form
  # - V0 Returns the code in numerical form
  # - V1 Full-word result codes
  if [[ $hcmd == 'V' ]]; then
    if [[ $hparm == '' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '0' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '1' ]]; then resultverbose=1; result=0; fi
  fi

  # ATXn Extended result codes
  # - X0 Disable extended result codes (Hayes Smartmodem 300 compatible result codes)
  # - X1 Add connection speed to basic result codes (e.g. CONNECT 1200)
  # - X2 Add dial tone detection (preventing blind dial, and sometimes preventing ATO)
  # - X3 Add busy signal detection
  # - X4 Add both busy signal and dial tone detection
  if [[ $hcmd == 'X' ]]; then
    if [[ $hparm == '' ]]; then resultverbose=1; result=0; fi
    if [[ $hparm == '0' ]]; then resultverbose=1; result=0; fi
    if [[ $hparm == '1' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '2' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '3' ]]; then resultverbose=0; result=0; fi
    if [[ $hparm == '4' ]]; then resultverbose=0; result=0; fi
  fi

  # ATZ Reset modem
  # - Zn  Restore stored profile n
  if [[ $hcmd == 'Z' ]]; then echoser=1; resultverbose=1; carrierdetect=0; result=0; fi

  # AT&Cn Carrier-detect
  # - &C0 Force DCD signal active
  # - &C1 DCD signal indicates true state of remote carrier signal
  if [[ $hcmd == '&C' ]]; then
    if [[ $hparm == '' ]]; then result=0; carrierdetect=0; fi
    if [[ $hparm == '0' ]]; then result=0; carrierdetect=0; fi
    if [[ $hparm == '1' ]]; then result=0; carrierdetect=1; fi
  fi

  # AT&Dn Data Terminal Ready settings
  # - &D0 Modem ignores DTR
  # - &D1 Go to command mode on ON-to-OFF DTR transition.
  # - &D2 Hang up on DTR-drop and go to command mode
  # - &D3 Reset (ATZ) on DTR-drop. Modem hangs up.
  if [[ $hcmd == '&D' ]]; then
    if [[ $hparm == '' ]]; then result=0; fi
    if [[ $hparm == '0' ]]; then result=0; fi
    if [[ $hparm == '1' ]]; then result=0; fi
    if [[ $hparm == '2' ]]; then result=0; fi
    if [[ $hparm == '3' ]]; then result=0; fi
  fi

  # AT&F Restore factory settings
  # - &Fn Use profile n
  if [[ $hcmd == '&F' ]]; then echoser=1; resultverbose=1; carrierdetect=0; result=0; fi

  # AT&K DTE - MODEM Flow control
  # - &K0 Local flow control off
  # - &K1 Not used
  # - &K2 Not used
  # - &K3 RTS/CTS
  # - &K4 XON/XOFF
  # - &K5 Transparent XON/XOFF
  # - &K6 RTS/CTS and XON/XOFF
  if [[ $hcmd == '&K' ]]; then result=0; fi

  # AT&Sn DSR Override
  # - &S0 DSR will remain on at all times.
  # - &S1 DSR will become active after answer tone has been detected and inactive after the carrier has been lost
  if [[ $hcmd == '&S' ]]; then
    if [[ $hparm == '' ]]; then result=0; fi
    if [[ $hparm == '0' ]]; then result=0; fi
    if [[ $hparm == '1' ]]; then result=0; fi
  fi
}

# MAIN LOOP
while [ "$continue" != "1" ]; do
  charhex=`head -c 1 /dev/$serport | xxd -p -`
  char="`echo -e "\x$charhex"`"

  #ECHO SERIAL INPUT TO TTY
  echo -n "$char"

  #ECHO SERIAL INPUT
  if [ "$echoser" = "1" ]; then echo -n "$char" > /dev/$serport; fi

  #CHECK IF NEWLINE IS SENT
  if [ "$charhex" = "0d" -o "$charhex" = "0a" ]; then
    line=$buffer
    # PARSE COMMAND
    cmd=`echo -en $buffer | tr a-z A-Z`
    buffer=
    char=

    #NEWLINE SENT - ECHO NEWLINE TO CONSOLE
    if [ "$echoser" = "0" ]; then echo; fi
    if [ "$echoser" = "1" ]; then sendtty "\n"; fi

    #
    # --- HAYES EMULATION ---
    #
    if [[ $cmd == AT* ]]; then
      # Attention! Client issued an AT command
      #
      # default to error result code, if command not recognized
      result=4; resultc=0

      if [[ $cmd == AT ]]; then result=0; fi

      # Get full hayes string and parse it
      seq=`echo $cmd |cut -b3-`
      ptr=1
      until [ $ptr -gt 64 ]; do
        hchar=$(echo "$seq" |cut -b$ptr)
        #sendtty "$ptr $hchar\n"
        if [[ $hchar =~ [A-Z\&] ]]; then
          if [[ $hchar == '&' ]]; then
            hcmd="$hchar"
            ptr=$((ptr+1))
            hchar=$(echo "$seq" |cut -b$ptr)
            if [[ $hchar =~ [A-Z] ]]; then
              hcmd="$hcmd$hchar"
              until [ $hdone ]; do
                ptr=$((ptr+1))
                hchar=$(echo "$seq" |cut -b$ptr)
                if [[ $hchar =~ [0-9] ]]; then
                  hparm="$hparm$hchar"
                else
                  ptr=$((ptr-1))
                  hdone=1
                fi
              done
            fi
          elif [[ $hchar =~ [A-CE-Z] ]]; then
            hcmd="$hcmd$hchar"
            until [ $hdone ]; do
              ptr=$((ptr+1))
              hchar=$(echo "$seq" |cut -b$ptr)
              if [[ $hchar =~ [0-9] ]]; then
                hparm="$hparm$hchar"
              else
                ptr=$((ptr-1))
                hdone=1
              fi
            done
          elif [[ $hchar == 'D' ]]; then
            hcmd="$hcmd$hchar"
            until [ $hdone ]; do
              ptr=$((ptr+1))
              hchar=$(echo "$seq" |cut -b$ptr)
              if [[ $hchar =~ [0-9PRT,!] ]]; then
                hparm="$hparm$hchar"
              else
                ptr=$((ptr-1))
                hdone=1
              fi
            done
          fi
        fi
        ptr=$((ptr+1))
        if [[ ! -z "$hcmd" ]]; then
          dohayes
          # preserve error if one was encountered
          if [[ $result == '4' ]]; then resultc='4'; fi
        else
          break
        fi
        hcmd=""
        hparm=""
        hdone=""
      done

      if [[ $resultc == '4' ]]; then result='4'; fi

      # ATD Dial number
      if [[ ! -z "$number" ]]; then
        if [[ $resultverbose == 1 ]]; then sendtty "RINGING\n"; fi
        sleep 2
        if [ -f "$number.sh" ]; then
          if [[ $resultverbose == 1 ]]; then sendtty "CONNECT $baud\n"; else sendtty "1\n"; fi
          # Assert DCD when carrier detection is turned on (for Trumpet Winsock)
          if [[ $carrierdetect == 1 ]]; then exec 99>&-; fi

          # Tell the terminal to use CR/LF for newlines instead of just CR.
          echo -en "\x1b[20h" > /dev/$serport

          # Run script
          #/sbin/getty -8 -L $serport $baud $TERM -n -l "./$number.sh"
          ./$number.sh

          if [[ $carrierdetect == 1 ]]; then exec 99<>/dev/$serport; fi

          # Reset serial settings
          ttyinit
          result=3
        else
          # Phone number is valid, but no internal script by that name exists
          result=3
        fi
        number=""
      fi

      #
      # --- PRINT RESULT CODE ---
      #
      if [[ $resultverbose == 0 ]]; then
        sendtty "$result\n";
      elif [[ $resultverbose == 1 ]]; then
        if [[ $result == 0 ]]; then sendtty "OK\n"; fi
        if [[ $result == 1 ]]; then sendtty "CONNECT\n"; fi
        if [[ $result == 2 ]]; then sendtty "RING\n"; fi
        if [[ $result == 3 ]]; then sendtty "NO CARRIER\n"; fi
        if [[ $result == 4 ]]; then sendtty "ERROR\n"; fi
        if [[ $result == 5 ]]; then sendtty "CONNECT 1200\n"; fi
        if [[ $result == 6 ]]; then sendtty "NO DIALTONE\n"; fi
        if [[ $result == 7 ]]; then sendtty "BUSY\n"; fi
        if [[ $result == 8 ]]; then sendtty "NO ANSWER\n"; fi
      fi
    fi

    if [[ $cmd = "HELP" ]] || [[ $cmd = "?" ]]; then
      sendtty "Command Reference for Virtual Modem Bootstrap v$vmodver\n"
      sendtty "\n"
      sendtty "General commands:\n"
      sendtty "HELP.......Display this help\n"
      sendtty "LOGIN......Drop to shell\n"
      sendtty "SETUP......Change settings\n"
      sendtty "EXIT.......End this script\n"
      sendtty "\n"
      sendtty "Common Hayes commands:\n"
      sendtty "AT.........Tests serial connection, prints OK if successful\n"
      sendtty "ATE0/ATE1..Switch terminal echo 0-off or 1-on\n"
      sendtty "ATD#.......Fork #.sh and output on terminal\n"
      sendtty "ATD1.......Fork 1.sh, which by default starts a PPP connection\n"
      sendtty "ATZ........Reset modem settings\n"
      sendtty "\n"
      sendtty "To establish connection over PPP, dial 1 (ATDT1)\n"
      sendtty "\n"
      sendtty "READY.\n"
    fi

    if [[ $cmd = "SETUP" ]]; then
      while true; do
        # Display menu
        sendtty "\n"
        sendtty "System Setup\n"
        sendtty "============\n"
        sendtty "1. Change Wireless Network settings\n"
        sendtty "2. Exit\n"
        sendtty "Enter your selection: "
        # Read user input
        readtty selection

        # Wireless network settings
        if [[ "$selection" == "1" ]]; then
          while true; do
            sendtty "\n"
            sendtty "Wi-Fi Settings\n"
            sendtty "==============\n"
            sendtty "1. Connect to new Wi-Fi network\n"
            sendtty "2. Modify password for current Wi-Fi network\n"
            sendtty "3. Disconnect from current Wi-Fi network\n"
            sendtty "4. Display current Wi-Fi connection status\n"
            sendtty "5. Exit\n"
            sendtty "Enter your selection: "
            # Read user input
            readtty selection
            # Connect to new Wi-Fi network
            if [[ "$selection" == "1" ]]; then
              sendtty "Enter SSID: "
              readtty ssid
              sendtty "Enter password: "
              readtty password
              sudo wpa_cli -i wlan0 remove_network 0
              sudo wpa_cli -i wlan0 add_network
              sudo wpa_cli -i wlan0 set_network 0 ssid "\"$ssid\""
              sudo wpa_cli -i wlan0 set_network 0 psk "\"$password\""
              sudo wpa_cli -i wlan0 select_network 0
              sudo wpa_cli -i wlan0 enable_network 0
            # Modify password for current Wi-Fi network
            elif [[ "$selection" == "2" ]]; then
              sendtty "Enter new password: "
              readtty password
              sudo wpa_cli -i wlan0 set_network 0 psk "\"$password\""
            # Disconnect from current Wi-Fi network
            elif [[ "$selection" == "3" ]]; then
              sendtty "Disconnecting from current Wi-Fi network\n"
              sudo wpa_cli -i wlan0 disable_network 0
            # Display current Wi-Fi connection status
            elif [[ "$selection" == "4" ]]; then
              status=$(sudo wpa_cli -i wlan0 status)
              sendtty "\n"
              sendtty "Wi-fi connection status\n"
              sendtty "=======================\n"
              sendtty "$status"
              sendtty "\n"
            # Exit
            elif [[ "$selection" == "5" ]]; then
              break
            # Invalid selection
            else
              sendtty "Invalid selection. Please try again.\n"
            fi
          done
        # Exit
        elif [[ "$selection" == "2" ]]; then
          sendtty "Exited setup\n"
          sendtty "READY.\n"
          break
        # Invalid selection
        else
          sendtty "Invalid selection. Please try again.\n"
        fi
      done
    fi


    # LOGIN  -  FORK LOGIN SESSION
    if [[ $cmd == LOGIN ]]; then
      exec 99>&-
      /sbin/getty -8 -L $serport $baud $TERM
      ttyinit
      exec 99<>/dev/$serport
      sendtty "\n"; sendtty "READY.\n"
    fi

    # EXIT  -  EXIT SCRIPT
    if [ "$cmd" = "EXIT" ]; then sendtty "OK\n"; continue="1"; fi
  fi
  buffer=$buffer$char
done

#Close serial port
exec 99>&-
</code>

===== 1.sh =====
1.sh is a virtual phone number used to establish a PPP connection. 1.sh can be dialed by issuing they Hayes dial command "ATDT1" using vmodem.sh. 1.sh is only a redirect script and will actually just run ppp.sh which will initiate the actual PPP connection.

<code bash 1.sh>
#!/bin/bash
#
./ppp.sh
</code>

===== ppp.sh =====
This script will initiate a PPP session and will present a fake login shell, but will not wait around for user input. The fake login shell is in place for compatibility with Trumpet Winsock 3.0, as it by default expects one, so we're fooling it to make it think that it's logging on. It will then proceed when it receives the expected printouts. The built-in dial-up connection in Windows 95/98/Me by default do not expect a login prompt unless specifically told to do so.

When Trumpet Winsock is in PPP mode, by default it will expect the following output after dialing the ISP's number and establishing a connection: 
  * A username prompt, matched by Trumpet with the text "sername:"
  * A password prompt, matched by Trumpet with the text "ssword:"
  * A command prompt, matched by Trumpet with the character ">"

This script has been tested with the default installation of Trumpet Winsock 3.0 revision D with PPP mode switched on. This script has also been tested with the default dial-up utility of Windows 95 and Windows 98 with PPP enabled. 

I've added a parameter to send an LCP echo to the client to test if the connection is still up. If the connection has abruptly been closed, pppd will know this by not receiving an echo reply, and will exit and relinquish control back to the vmodem.sh script. The only reason the timeout is in there, is because it seems like Trumpet Winsock 3.0 doesn't know how to tell pppd to terminate a PPP session from within a PPP session, and it will just hang up the call. As a result, pppd daemon will be left running indefinitely and won't ever give control back to vmodem. This is obviously not preferred, so LCP echo is added to let pppd know when the link has been cut. If you can think of better ways to accomplish this check, feel free to send tips on how to improve the script.

<code bash ppp.sh>
#!/bin/bash
# RUN PPPD DAEMON
#
# Oliver Molini 2021
# 
# Billy Stoughton II for bug fixes and contributions
#
# Licensed under Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License
# https://creativecommons.org/licenses/by-nc-sa/4.0/
#
# Note on PPPD settings:
# - Make sure the noauth option is set (instead of auth)
# - Make sure DNS servers are defined (add ms-dns 1.2.3.4 twice)
#

# Variable: etherp
# Override the ethernet device to use to connect to your network.
# This is set in vmodem.sh, but can be overridden here.
#
# Default:    #etherp=eth0 (commented out)
#etherp=eth0

# Variable: lcpidle
# Specifies the idle timeout period in seconds for lcp-echo-interval.
# This is to ensure that pppd will not run indefinitely after sudden
# hangup and will relinquish control back to the vmodem.sh.
#
# Default:    lcpidle=5
lcpidle=10

#
# Trumpet Winsock 3.0 revision D for Windows 3.1
# by default requires a fake login shell.
#
# Windows 95 and 98 will not care for a login shell
# unless specifically told to expect one.
#

sleep 2
sendtty "\n\n`uname -sn`****\n\n"
sendtty  "Username: "; sleep 1; sendtty "\n"
sendtty  "Password: "; sleep 1; sendtty "\n"
sendtty  "Starting pppd...\n"
sendtty  "PPP>"
# End of fake login prompt.

# Set the kernel to router mode
sysctl -q net.ipv4.ip_forward=1

# Share eth0 over ppp0
iptables -t nat -A POSTROUTING -o $etherp -j MASQUERADE
iptables -t filter -A FORWARD -i ppp0 -o $etherp -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -t filter -A FORWARD -i $etherp -o ppp0 -j ACCEPT

# Run PPP daemon and establish a link.
pppd noauth nodetach local lock lcp-echo-interval $lcpidle lcp-echo-failure 3 proxyarp ms-dns 8.8.4.4 ms-dns 8.8.8.8 10.0.100.1:10.0.100.2 /dev/$serport $baud

# Flush iptables
iptables -t filter -F FORWARD
iptables -t nat -F POSTROUTING

printf "\nPPP link terminated.\n"
</code>

===== 2.sh =====
This example script demonstrates how easy it is to make simple dial-up services, such as BBS's. To call this script, from the serial console, type "ATD2".

<code bash 2.sh>
#!/bin/bash
#

sendtty "Hello World Demo Box!\n"
sendtty "---------------------\n"
sendtty "\n"
sendtty "You have just successfully dialed this virtual box!\n"
sendtty "\n"
sendtty "Please enter your name: \n"
readtty username
sendtty "\n"
sendtty "Hello, $username!\n"
sendtty "\n"
sendtty "Thank you for visiting! Bye!\n"
sleep 2

</code>

===== 3.sh =====
This example script allows VT100 compatible terminal access to the web by way of running lynx as soon as the number "3" is dialed with "ATD3". It demonstrates how to add a Linux based web browser for simple terminals.

<code bash 3.sh>
#!/bin/bash
#
sendtty "Terminal type set to $TERM. Running Lynx ..."
lynx
</code>