Overview

liblnpp — a reference implementation of the LNPP protocol. Has an interface suited for implementing both clients and servers. Implemented with 100% compliance to the LNPP specification.

Features

• Implemented in C using C23 standard.
• Very minimalistic (<700 LOC).
• No dependencies except libc.
• Header file doesn't depend on libc.
• Header file is compatible with C11 standard.
• Doesn't do any system calls. Therefore, doesn't do networking nor memory allocations, allowing to use library with any IO and memory model.
• Only implements message parsing/rendering part, keeping things simple.

Building

This project consists of the following files:

• "lnpp.h" — header file for library users;
• "lnpp.c" — implementation of "lnpp.h";
• "test_lnpp.c" — unit tests for "lnpp.h" utilizing CUnit.

This project uses Meson build system.

Although even if you don't have/don't want to use Meson, building liblnpp without that is extremely simple. Simply compile "lnpp.c" to get a usable .o file for your project, or a shared library:

cc lnpp.c -std=c23 -D_DEFAULT_SOURCE -c -o lnpp.o
cc lnpp.c -std=c23 -D_DEFAULT_SOURCE -shared -o liblnpp.so

Usage

Just include the header file:

#include "lnpp.h"

And link the library:

cc main.c -c -o main.o # Let main.c be your program
cc main.o lnpp.o -o main # If compiled as an object
cc main.o -o main -llnpp # If installed as a shared library
cc main.o -o main `pkg-config --libs --cflags lnpp` # Let pkgconf determine required flags

Documentation

About the most important definitions in "lnpp.h":

struct lnpp_request, struct lnpp_response

Data structures representing LNPP messages in memory.

lnpp_request_packetlen, lnpp_response_packetlen

Calculate how many bytes required to encode a UDP packet for a message.

lnpp_request_validate, lnpp_response_validate

Check if numeric values in a message are valid according to LNPP specification.

lnpp_request_encode, lnpp_response_encode

Render message in a UDP packet. Write bytes in a user provided pointer, assuming that it points to a required amount of memory allocated. Return amount of bytes written.

lnpp_request_decode, lnpp_response_decode

Parse message out of UDP packet. Return code signifies either success or one of the errors.

LNPP_REQUEST_MAX_PACKETLEN, LNPP_RESPONSE_MAX_PACKETLEN

Max possible length of a UDP packet for any message.

Authors

• Lich author@lch361.net

Feel free to message me if you have any questions.