The default package available from the Debian repository is enable just for the MQTT protocol. These are the commands to install it.
apt-get update apt-get install mosquitto
wget http://repo.mosquitto.org/debian/mosquitto-repo.gpg.key sudo apt-key add mosquitto-repo.gpg.key cd /etc/apt/sources.list.d/ sudo wget http://repo.mosquitto.org/debian/mosquitto-jessie.list sudo apt-get update sudo apt-get dist-upgrade
Create a new file called /etc/mosquitto/conf.d/websocket.conf with this content:
listener 1883 listener 1884 protocol websockets
service mosquitto restart
To test if Mosquitto is working on your board make a subscription to the broker to receive all messages:
mosquitto_sub -h localhost -t "#" -v
Then open another therminal session and send a messagge to the topic "test":
mosquitto_pub -h localhost -t "test" -m "Hello world!"
You will see the message received.