pktfmt 0.2.0

Generate RFC-style ASCII packet diagrams from field definitions

pktfmt

Generate RFC-style ASCII packet diagrams from field definitions.

A modern, pip-installable alternative to protocol that works on Windows and modern Python.

Installation

pip install pktfmt

Features

• 20+ built-in protocols - TCP, UDP, IP, DNS, and more
• Custom packet definitions - inline format or JSON files
• Unicode box drawing - pretty output for modern terminals
• Variable-length fields - with distinct visual styling
• Cross-platform - works on Windows, macOS, and Linux
• Modern Python - supports Python 3.8+

Quick Start

# Show a built-in protocol
pktfmt tcp

# List all available protocols
pktfmt --list

# Custom inline format
pktfmt "Type:16,Length:16,Payload:*"

# Pretty Unicode output
pktfmt udp --unicode

Usage

Built-in Protocols

pktfmt tcp                    # TCP header
pktfmt udp                    # UDP header
pktfmt ipv4                   # IPv4 header
pktfmt dns                    # DNS header
pktfmt --list                 # Show all 20+ protocols

Custom Inline Format

pktfmt "Type:16,Length:16,Payload:*"

Output:

 0                  1                  2                  3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              Type             |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
:                            Payload                            :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

JSON File Format

pktfmt packet.json

{
  "name": "MyPacket",
  "fields": [
    {"name": "Type", "bits": 16},
    {"name": "Length", "bits": 16},
    {"name": "Payload", "bits": "*"}
  ]
}

Unicode Output

pktfmt udp --unicode

 0                  1                  2                  3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
┌───────────────────────────────┬───────────────────────────────┐
│          Source Port          │        Destination Port       │
├───────────────────────────────┼───────────────────────────────┤
│             Length            │            Checksum           │
├───────────────────────────────────────────────────────────────┤
┊                              Data                             ┊
└───────────────────────────────────────────────────────────────┘

Bold Unicode Style

pktfmt tcp --style bold

Options

pktfmt <input> [options]

Options:
  -l, --list              List all built-in protocols
  -b, --bits-per-row N    Bits per row (default: 32)
  -s, --style STYLE       Output style: ascii, unicode, bold
  -u, --unicode           Shortcut for --style unicode
  --no-ruler              Omit the bit number header
  -v, --version           Show version

Field Syntax

• Name:N - Fixed-width field of N bits
• Name:* - Variable-length field (rendered with : or ┊ borders)

Built-in Protocols

Layer	Protocols
Layer 2	ethernet, 802.1q, arp
Layer 3	ipv4, ipv6, icmp, icmpv6
Layer 4	tcp, udp, sctp
Application	dns, dhcp, ntp, tls
Tunneling	gre, vxlan, quic
Industrial	modbus, dnp3

Why pktfmt?

• Actually installs via pip - protocol requires manual setup.py installation
• Works on modern Python - protocol uses deprecated distutils
• Works on Windows - proper UTF-8 handling
• Actively maintained - PRs get merged
• Unicode support - pretty box drawing characters
• More protocols - 20+ built-in, vs ~10 in protocol

License

MIT