Add bare echoing telnet server

justfile

@@ -9,3 +9,6 @@ test:
     uv run pytest
 
 check: lint typecheck test
+
+run:
+    uv run python -m mudlib

mud.tin

@@ -0,0 +1,3 @@
+#NOP TinTin++ config for connecting to the MUD server
+#split 0 1
+#session mud localhost 6789

pyproject.toml

@@ -12,6 +12,7 @@ dev = [
     "ruff",
     "pyright",
     "pytest",
+    "pytest-asyncio",
 ]
 
 [build-system]

src/mudlib/__main__.py

@@ -0,0 +1,8 @@
+"""Main entry point for running the MUD server."""
+
+import asyncio
+
+from mudlib.server import run_server
+
+if __name__ == "__main__":
+    asyncio.run(run_server())

src/mudlib/server.py

@@ -0,0 +1,54 @@
+"""Telnet server for the MUD."""
+
+import asyncio
+from typing import cast
+
+import telnetlib3
+
+PORT = 6789
+
+
+async def shell(
+    reader: telnetlib3.TelnetReader | telnetlib3.TelnetReaderUnicode,
+    writer: telnetlib3.TelnetWriter | telnetlib3.TelnetWriterUnicode,
+) -> None:
+    """Shell callback that greets the player and echoes their input."""
+    # Cast to unicode variants since we're using encoding="utf8"
+    _reader = cast(telnetlib3.TelnetReaderUnicode, reader)
+    _writer = cast(telnetlib3.TelnetWriterUnicode, writer)
+
+    _writer.write("Welcome to the MUD!\r\n")
+    _writer.write("Type 'quit' to disconnect.\r\n\r\n")
+    await _writer.drain()
+
+    while not _writer.is_closing():
+        _writer.write("mud> ")
+        await _writer.drain()
+
+        inp = await _reader.readline()
+        if not inp:
+            break
+
+        command = inp.strip()
+        if command == "quit":
+            _writer.write("Goodbye!\r\n")
+            break
+
+        _writer.write(f"You typed: {command}\r\n")
+
+    _writer.close()
+
+
+async def run_server() -> None:
+    """Start the MUD telnet server."""
+    server = await telnetlib3.create_server(host="127.0.0.1", port=PORT, shell=shell)
+    print(f"MUD server running on 127.0.0.1:{PORT}")
+    print("Connect with: telnet 127.0.0.1 6789")
+
+    try:
+        while True:
+            await asyncio.sleep(3600)
+    except KeyboardInterrupt:
+        print("\nShutting down...")
+        server.close()
+        await server.wait_closed()

tests/test_server.py

@@ -0,0 +1,92 @@
+"""Tests for the server module."""
+
+import asyncio
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from mudlib import server
+
+
+def test_port_constant():
+    """Test that PORT is defined correctly."""
+    assert server.PORT == 6789
+    assert isinstance(server.PORT, int)
+
+
+def test_shell_exists():
+    """Test that the shell callback exists and is callable."""
+    assert callable(server.shell)
+    assert asyncio.iscoroutinefunction(server.shell)
+
+
+def test_run_server_exists():
+    """Test that run_server exists and is callable."""
+    assert callable(server.run_server)
+    assert asyncio.iscoroutinefunction(server.run_server)
+
+
+@pytest.mark.asyncio
+async def test_shell_greets_and_echoes():
+    """Test that shell greets the player and echoes input."""
+    reader = AsyncMock()
+    writer = MagicMock()
+    writer.is_closing.return_value = False
+    writer.drain = AsyncMock()
+    writer.close = MagicMock()
+
+    # Simulate user typing "hello" then "quit"
+    reader.readline.side_effect = ["hello\r\n", "quit\r\n"]
+
+    await server.shell(reader, writer)
+
+    # Check that welcome message was written
+    calls = [str(call) for call in writer.write.call_args_list]
+    assert any("Welcome" in call for call in calls)
+
+    # Check that input was echoed
+    assert any("hello" in call for call in calls)
+
+    # Check that goodbye was written
+    assert any("Goodbye" in call for call in calls)
+
+    # Check that close was called
+    writer.close.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_shell_handles_empty_input():
+    """Test that shell handles EOF gracefully."""
+    reader = AsyncMock()
+    writer = MagicMock()
+    writer.is_closing.return_value = False
+    writer.drain = AsyncMock()
+    writer.close = MagicMock()
+
+    # Simulate EOF
+    reader.readline.return_value = ""
+
+    await server.shell(reader, writer)
+
+    # Should close cleanly
+    writer.close.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_shell_handles_quit():
+    """Test that shell exits on quit command."""
+    reader = AsyncMock()
+    writer = MagicMock()
+    writer.is_closing.return_value = False
+    writer.drain = AsyncMock()
+    writer.close = MagicMock()
+
+    reader.readline.return_value = "quit\r\n"
+
+    await server.shell(reader, writer)
+
+    # Check that goodbye was written
+    calls = [str(call) for call in writer.write.call_args_list]
+    assert any("Goodbye" in call for call in calls)
+
+    writer.close.assert_called_once()

uv.lock

@@ -32,6 +32,7 @@ dependencies = [
 dev = [
     { name = "pyright" },
     { name = "pytest" },
+    { name = "pytest-asyncio" },
     { name = "ruff" },
 ]
 
@@ -42,6 +43,7 @@ requires-dist = [{ name = "telnetlib3" }]
 dev = [
     { name = "pyright" },
     { name = "pytest" },
+    { name = "pytest-asyncio" },
     { name = "ruff" },
 ]
 
@@ -110,6 +112,19 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/3b/ab/b3226f0bd7cdcf710fbede2b3548584366da3b19b5021e74f5bde2a8fa3f/pytest-9.0.2-py3-none-any.whl", hash = "sha256:711ffd45bf766d5264d487b917733b453d917afd2b0ad65223959f59089f875b", size = 374801, upload-time = "2025-12-06T21:30:49.154Z" },
 ]
 
+[[package]]
+name = "pytest-asyncio"
+version = "1.3.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "pytest" },
+    { name = "typing-extensions", marker = "python_full_version < '3.13'" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/90/2c/8af215c0f776415f3590cac4f9086ccefd6fd463befeae41cd4d3f193e5a/pytest_asyncio-1.3.0.tar.gz", hash = "sha256:d7f52f36d231b80ee124cd216ffb19369aa168fc10095013c6b014a34d3ee9e5", size = 50087, upload-time = "2025-11-10T16:07:47.256Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/e5/35/f8b19922b6a25bc0880171a2f1a003eaeb93657475193ab516fd87cac9da/pytest_asyncio-1.3.0-py3-none-any.whl", hash = "sha256:611e26147c7f77640e6d0a92a38ed17c3e9848063698d5c93d5aa7aa11cebff5", size = 15075, upload-time = "2025-11-10T16:07:45.537Z" },
+]
+
 [[package]]
 name = "ruff"
 version = "0.15.0"