LightMQTT is a MQTT 3.1.1 client library written in pure C and designed to work with both embedded and large systems.
- Fully asynchronous (no threads)
- Supports QoS 0, 1 and 2 messages
- No
malloc's. Pure C. (Only dependencies arestddef.handstring.h) - Handles large payloads in both directions
- Minimal memory requirements, even with large payloads (about 2 KB)
Examples are available under examples.
pingpong is a client which echoes a given message back and forth,
demonstrating the usage of subscriptions and exchanging of QoS 2 messages. To
test it first start the pong side:
examples/pingpong -h 127.0.0.1 -i pong -t ping
The arguments given mean it'll connect with client id pong to a broker running at the default port (1883) on host 127.0.0.1, expecting the other side to be identified as ping. Then start the ping side in another terminal:
examples/pingpong -h 127.0.0.1 -i ping -t pong -m test
Besides having the -i and -t arguments reversed, the second instance also passes a message (test) to be sent to the other side after the initialization is completed (that's required and won't work if given to the first instance).
Instead of a string you can also give the program a file with -f. If the file
is larger than the message buffer (message_payload, currently 256 bytes)
pingpong will use temporary files, created via mkostemp, to transfer it.
Try pingpong with a large file (tens of megabytes) and a fast, local broker
(like ActiveMQ Apollo) and check how
little CPU and memory it uses!
reconnect maintains a connection to the broker using a given keep alive
interval. If the connection is dropped the client reconnects without
reinitializing the internal data (i.e. the session state is preserved). For
example, to connect to host 127.0.0.1 and send keep alive packets every 5
seconds execute:
examples/reconnect -h 127.0.0.1 -i reconnect -k 5
To contribute:
- Fork the project on Github
- Checkout a new branch
- Write one or more tests evidencing the bug or the features you want
- Make your changes
- Send a pull request
Or open an issue on Github explaining clearly how to reproduce the bug or the motivation for the feature.
To build the project you need
Autoconf Archive and
Check. On Linux Ubuntu/Debian/Mint they are
available via apt:
$ apt install autoconf-archive check
Then execute:
$ autoreconf --install
$ mkdir build && cd build
$ ../configure
$ make && make check
See LICENSE.