pydhcp

A pure-Python DHCPv4 library with a server, a client, a relay agent and a capture tool, each in a blocking and an asyncio form over typed messages and options. It targets Python 3.9 and newer: packet parsing and the structured formats are portable, while actually serving DHCP still depends on OS socket permissions and platform-specific UDP behavior.

• Packet parsing and construction: every DHCPv4 message, a DHCPOptionCode member and a typed codec for each IANA option, and a JSON form of every message (YAML, TOML and INI with the pktcap extra). Liberal on receive, strict on send.
• Server base: lease and option policy hooks, an in-memory and a file lease backend, and a threaded and an asyncio driver (DHCPServer, AsyncDHCPServer) over one core, so a fix to the rules reaches both.
• Relay agent: DHCPRelay forwards client traffic to upstream servers per RFC 1542 / RFC 2131 §4.1, with hop-limit loop protection and optional RFC 3046 option-82 tagging.
• Packet client and capture: DHCPClient builds and sends the client messages and runs a DORA exchange; sniff_dhcp and the pydhcp capture command (pktcap's, with the pktcap extra) record, filter, replay and hand each packet to a hook.

Installation

pip install pydhcp

The library (packets, options, server, client, relay) needs nothing else. What else you ask of it is an extra, one for each capability:

Extra	Adds	Needed for
cli	duho	the pydhcp command (python -m pydhcp)
pktcap	pktcap	captures (pydhcp capture, pydhcp replay, sniff_dhcp) and a message or a lease as YAML, TOML or INI text (which also needs pktcap[yaml] or pktcap[toml])

For example pip install "pydhcp[cli,pktcap]". JSON needs no extra.

30-second tour

from pydhcp.server import DHCPServer

with DHCPServer(listen="*") as server:    # binds; does not serve yet
    server.serve_forever()                # until shutdown(); Ctrl-C raises KeyboardInterrupt

start() receives on a daemon thread instead and returns. shutdown() ends either and never blocks, so a handler may call it; wait_closed() blocks until receiving has stopped; close() (which leaving the with block calls) does both and then releases the sockets. Closed is final, and the library installs no signal handler.

from pydhcp.client import DHCPClient

client = DHCPClient(listen=("127.0.0.1", 6768))
discover = client.build_discover(b"\x00\x11\x22\x33\x44\x55")
client.send(discover, dst="127.0.0.1", port=6767)

DHCPClient is intentionally packet-level tooling; it does not configure the operating system network stack.

pydhcp capture --listen 127.0.0.1:6767 --filter msg_type=DHCPDISCOVER --output -
pydhcp --config server.toml server

Learn more

• API reference: the message, the options, the roles and the capture tools, from their docstrings.
• Examples: a custom lease backend, a custom server policy, a config file, the packet client and a full DORA exchange.
• Common DHCP options: typed examples for the options most sites set.
• Conformance: what is compared with dnsmasq and ISC dhclient, what each role covers and the differences.
• Deployment and Troubleshooting.
• FAQ and the changelog.