Internet Modem
Telnet to modem emulator for Windows
Current Version:


Written in Visual Basic 2005 Express Edition
Updated with Visual Basic 2015 Community Edition
Requires Microsoft .NET Framework 4.5

View the source code here:

I've changed the AT command parser so that it can accept multiple commands. It should ignore all commands it doesn't require and return a result code of "0" or "OK". I've also added a few AT Commands. See the table below to see the complete list of supported commands.

Also added is the ability to see the AT commands sent from your terminal, and the Result Codes returned to your terminal. Take a look at the ".ini" file for these settings.

One problem i've found is that it doesn't always detect a remote telnet disconnect.  It seems to work good otherwise. Please let me know if you find any problems or bugs with it (explain it so I can reproduce the anomaly).

ATDT <IP Address or URL>[:<port number>] Establishes a TCP connection to the specified host on the specified port. If a port is not specified, port 23 is assumed.
ATE Echo mode off (ATE0) or on (ATE1, the default)
ATH Disconnects the network session
ATI Displays modem version information
ATQ Result codes on (ATQ0, the default) or off (ATQ1)
ATS0 ATS0=0 will cause the program to send RING to the serial port when it receives a network connection request. The connected serial device (BBS) must reply with the ATA string before the program sends the CONNECT message.

ATS0=1 will cause the program to automatically accept network connections (the default) and send the CONNECT code to the serial port.

ATV Numeric codes (ATV0, the default) or Text codes (ATV1)
AT&V Displays current modem settings
A/ Repeat last AT Command sequence
ATD Re-dial last system dialed

A picture of my Apple II running ProTERM 3.1, chatting on

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