Simon Marsh
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208 lines
5.1 KiB
Markdown
208 lines
5.1 KiB
Markdown
---
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title: "Modem Emulator"
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geekdocDescription: "Modem Emulator Service"
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weight: 20
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---
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No modem ? no problem.
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If you don't have a physical modem you can still get that retro vibe by
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accessing dn42 using the modem emulator service. This service presents a
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series of TCP/IP ports that emulate a subset of the Hayes AT command set
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and which are speed limited to specific baud rates. The modem can dial
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directly to the fr-par1 shell service for that CLI experience, or get
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full dn42 access via a PPP session.
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The service is intended to be used as a fake serial port in a retro VM or
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connected to directly using a serial terminal.
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## Accessing the modem emulator service
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- dialup.burble.dn42:_(10000 + baud/100)_
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The modem emulator is accessed by connecting to dialup.burble.dn42
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on ports corresponding to specific baud rates, as detailed in the table
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below.
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| Port | BAUD | Port | BAUD | Port | BAUD |
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|:--|:--|:--|:--|:--|:--|
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| _10003_ | 300 | _10012_ | 1200 | _10024_ | 2400 |
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| _10048_ | 4800 | _10096_ | 9600 | _10144_ | 14400 |
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| _10192_ | 19200 | _10288_ | 28800 | _10336_ | 33600 |
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| _10560_ | 56000 | _11150_ | 115000 |
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{{<hint info>}}
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Low baud rates give a great experience when using a serial terminal and
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the shell service but aren't so much fun when using PPP. Conversely, using
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a serial terminal and higher baud rates is a bit dull and they are better
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suited to the PPP service.
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{{</hint>}}
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The emulated modem is able to dial two services depending on the number used.
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| Dial Number | Service |
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|:--|:--|
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|54311|fr-par1 shell server|
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|4242|PPP dialup service|
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## Dialling the fr-par1 shell server
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Use a terminal emulator and dial **54311** to access the fr-par1 shell server.
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Once the modem connects, use your burble.dn42 username and password to log in.
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{{<hint info>}}
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You can set a burble.dn42 password using the [services portal](https://svc.burble.dn42).
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{{</hint>}}
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{{<hint info>}}
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Don't forget to set a terminal type once you've logged in, e.g. `export TERM=vt102`
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{{</hint>}}
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## Dialing the PPP server
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- Dial **4242** to access the PPP server.
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- Use username: *dn42*, password: *dn42* to log in.
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- Once you see the PPP initiation string, connect your PPP client.
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- PPP authentication should not be required.
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## Example shell session using socat and minicom
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Example on how to connect to the shell server using socat and minicom at 2400 baud
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```text
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$ socat -d -d pty,rawer tcp:dialup.burble.dn42:10024 &
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...
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... socat[xxx] N PTY is /dev/pts/2
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...
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$ minicom -D /dev/pts/2
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```
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Within minicom type **ATDT54311** to dial the shell server.
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```text
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Welcome to minicom 2.8
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OPTIONS: I18n
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Port /dev/pts/2, 14:01:58
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Press CTRL-A Z for help on special keys
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ATDT54311
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CONNECT 2400
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Ubuntu 22.04.1 LTS
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shell-fr-par1 login:
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```
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You can now log in using your burble.dn42 username and password.
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## Example PPP connection using QEMU and Windows XP
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Add a virtual serial port to QEMU using `-chardev` and `-device`.
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e.g. for windows XP connecting at 115k
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```text
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qemu-system-i386 -enable-kvm -cpu host -m 1024 -vga std -device AC97 -hda winxp.img -chardev socket,id=bdn42,port=11150,host=dialup.burble.dn42,server=off -device pci-serial,chardev=bdn42
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```
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Create a PPP dialup connection with username dn42 and password dn42, enable the option
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to prompt for username and password on connect.
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Start the connection and when then chat box opens:
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- Type **ATDT4242** to dial the PPP service
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- Log in using username dn42 / password dn42
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- Hit continue when you see the PPP connect string
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<video src="/retro/xpconnect.webm" width="1024" autoplay="true" loop="true"></video>
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The following chat script provided by 04dco should provide automatic login for win95 onwards:
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```text
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;
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; This is a script file that automatically logs you in
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; to establish a dn42 dial-up PPP connection.
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;
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; Main entry point to script
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;
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proc main
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integer nTries = 3
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; This is the login prompt and timeout values
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string szLogin = "modem-server Login: "
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integer nLoginTimeout = 5
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; This is the password prompt and timeout values
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string szPW = "Password: "
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integer nPWTimeout = 5
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; This is the prompt once your password is verified
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string szPrompt = "Last login: "
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; Attempt to login at most 'nTries' times
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while 0 < nTries do
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; Wait for the login prompt before entering
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; the user ID, timeout after x seconds
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waitfor szLogin then DoLogin
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until nLoginTimeout
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TryAgain:
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transmit "^M" ; ping
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nTries = nTries - 1
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endwhile
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goto BailOut
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DoLogin:
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; Enter user ID
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transmit $USERID, raw
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transmit "^M"
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; Wait for the password prompt
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waitfor szPW until nPWTimeout
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if FALSE == $SUCCESS then
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goto TryAgain
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endif
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; Send the password
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transmit $PASSWORD, raw
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transmit "^M"
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; Wait for the prompt
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waitfor szPrompt
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goto Done
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BailOut:
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; Something isn't responding. Halt the script
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; and let the user handle it manually.
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set screen keyboard on
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halt
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Done:
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endproc
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```
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## Source code
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The modem emulator is a small golang server and the source code is available on the
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[burble.dn42 git server](https://git.burble.com/burble.dn42/modemulator)
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