Hayes modem emulation

Copperline provides an emulated Hayes-compatible AT command modem connected to the Amiga’s serial port. The modem bridges Amiga serial communication to TCP connections, enabling terminal programs (such as Term, NComm, or JR-Comm) and BBS software to dial Internet telnet BBSes or accept incoming connections.

The modem command interpreter supports standard Hayes AT commands as well as the AT* extension set popularized by the WiModem232.

Configuration¶

In the launcher:

1. Navigate to I/O Ports -> Serial Port.

2. Set Device / Mode to Modem.

3. Optionally configure a Listen address (for incoming calls) and the Telnet NVT translation toggle.

In copperline.toml:

[serial]
mode = "modem"
# listen = "0.0.0.0:2323"   # Bind port for incoming calls (optional)
# telnet = true             # Enable Telnet NVT translation at power-on

From the command line:

copperline --model A1200 --serial modem KICK31.ROM

Dialing outbound connections¶

In your Amiga terminal software, use standard AT dialing commands:

• ATD<hostname>:<port> or ATDT<hostname>:<port>: Connects to a TCP endpoint (e.g., ATDTbbs.example.com:23). If no port is specified, port 23 (telnet) is used.

• ATD<digits>: Looks up numeric numbers in the [serial.phonebook] configuration table:

[serial.phonebook]
"5551234" = "bbs.example.com:23"
"5555678" = "bbs2.example.com"

Result codes returned by the modem:

• CONNECT [baud]: Successful TCP connection established.

• BUSY: Target refused connection.

• NO CARRIER: Connection failed or disconnected.

Outbound dialing performs DNS resolution and TCP connection synchronously on the emulation thread (with a five-second timeout once resolved), which causes a brief pause in emulation while the connection is established.

Handling incoming calls¶

To allow inbound connections, specify a listening address with listen = "0.0.0.0:2323" (or via the launcher).

• When a remote host connects, the modem emits RING on the serial port every four seconds.

• Answer manually by sending ATA, or configure auto-answer using register S0 (e.g., ATS0=1 answers on the first ring).

• If an incoming call is not answered within 10 rings, it is disconnected.

• If a second connection arrives while a call is active, it is immediately rejected with a busy state.

Telnet NVT translation (AT*T1 / AT*T0)¶

Raw TCP connections pass 8-bit byte streams directly. For compatibility with telnet servers requiring RFC 854 option negotiation:

• AT*T1 (or telnet = true in configuration): Enables Telnet NVT negotiation. The modem responds to ECHO, SUPPRESS-GO-AHEAD, BINARY, TERMINAL-TYPE ("ANSI"), and NAWS (window size). It also handles IAC escaping (0xFF).

• AT*T0 (Default): Raw 8-bit binary transport. Use this mode for BBS systems transferring binary files with ZModem, XModem, or raw protocols.

WiModem232 command extensions¶

Settings modified via AT commands can be saved to persistent NVRAM using AT&W and recalled with ATZ. Factory defaults can be restored with AT&F.

S-registers¶

Unimplemented S-registers read as 0 and ignore writes.

RS-232 control lines¶

• DTR (AT&D): Under AT&D2 (default) and AT&D3, dropping DTR (e.g., closing the terminal software or resetting the serial port) hangs up the active TCP connection.

• DCD (AT&C): Carrier Detect asserts when a call is connected and drops in command mode. AT&C0 forces DCD permanently high.

• CTS / DSR: Permanently asserted.

• RI: Ring Indicator is signaled via serial RING text result codes.

Scripted session replay¶

For deterministic automated testing, CI, or demo playback, network calls can be replaced with scripted session recordings:

[serial]
mode = "modem"
session = "session.txt"

Directives in a session file:

# Session script example
accept
delay 0.5
send \r\nWelcome to the BBS\r\n
expect BYE\r
send \r\nNO CARRIER\r\n
close