MQTT / C / Node js

This is an example of how to build a project using a MQTT server over Node Js with C software.

Usage:

Test MQTT broker:

~/MQTT_C_NodeJs > sudo apt install npm nodejs
~/MQTT_C_NodeJs > mkdir ssl
~/MQTT_C_NodeJs > ./genKey.sh
...
~/MQTT_C_NodeJs > cd Nodejs
~/MQTT_C_NodeJs/NodeJs > npm install
~/MQTT_C_NodeJs/NodeJs > js index.js
web server listening on 4000
Mosca server is up and running
...

Open a web browser and go to the server web page, copy / paste the displayed cmd to a new term, that should work.

Test C publisher:

~/MQTT_C_NodeJs > sudo apt install libmosquitto-dev
~/MQTT_C_NodeJs > cd C
~/MQTT_C_NodeJs/C > ./Configure/config
~/MQTT_C_NodeJs/C > make
~/MQTT_C_NodeJs/C > ./bin/exec

The web page should add two msg to it's content:

C msg
C client stopped

On the Node Js term it should appear a new line:

MQTT: C_soft connected

SSL:

If you want to use SSL/TLS encryption for your software use ./genKey.sh.

Usage:

 > ./genKey.sh
 GCA:
Generating a 2048 bit RSA private key
........................................+++
.............+++
writing new private key to 'ssl/ca.key'
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:
-----
 Server:
Generating RSA private key, 2048 bit long modulus
................................+++
.........................................................................................+++
e is 65537 (0x10001)
Signature ok
subject=/C=FR/ST=FR/O=MyComagny/OU=DevLabServer/CN=ox223252_server
Getting CA Private Key
Enter pass phrase for ssl/ca.key:
 Client:
Generating RSA private key, 2048 bit long modulus
.........................................................................................+++
...........+++
e is 65537 (0x10001)
Signature ok
subject=/C=FR/ST=FR/O=MyComagny/OU=DevLabClient/CN=ox223252_client
Getting CA Private Key
Enter pass phrase for ssl/ca.key:

Inpired by mosquitto explanations.

Customize:

You should customize the keygen by changing this vars:

	C (contry)	ST (state)	L '(city)	O (organization)	OU (organization unit)	CN (comon name)
CA  (certification authority)	FR	France	Paris	MyCompagny	Sys admin	Honoré
SR  (server)	FR	France	Paris	MyServerManager	Data Admin	Michel
CL  (client)	FR	France	Paris	MyClient	Data Prod	Robert

MQTT over NodeJs:

By default the web server listening on port 4000, and MQTT server listening 1883 or 8883 for normal or secure mode.

You could change the mode by commenting a small part of code (lines 34 - 38).

secure: { 
	port: portMQTT_S,
	keyPath: SECURE_KEY,
	certPath: SECURE_CERT,
}

If this part is commented, the server will work without SSL / TLS encryption, else it'll work with that.

Before try to work with SSL you should generate keys.

The default page of this server will display the available commands what you can use for tests purpose.

MQTT ovec C:

By default this sender is configured to work with the given NodeJs server, and to send one message and a disconnection message.

If you want to work without SSL/TLS encryption you should comment line 64 to 69:

if ( mosquitto_tls_opts_set ( mosq, 1, NULL, NULL ) ||
	mosquitto_tls_set ( mosq, ca, NULL, cert, key, NULL ) ||
	mosquitto_tls_insecure_set ( mosq, true ) )
{
	return ( __LINE__ );
}

and change port line 32:

const int port = 8883;

to

const int port = 1883;

according to the Node Js broker.

Note that, if you want to send multiple msg form different part of a bigger code, you should add a tread with only one task, to execute periodically mosquitto_loop() function, this function will keep the connection working.