It is important that your script doesnвЂ™t proceed until the connection has been established.ДЇor quick demo scripts I use time.sleep() to wait, and give the connection time to be established. What is sure however is that there is a time delay between the connection being created, and the callback being triggered.

Bind callback to callback function (on_connect())Д«ecause the callback function is asynchronous you donвЂ™t know when it will be triggered.

Therefore the script generally looks like this. To process the callback you will need to run a loop.

4: Connection refused вЂ“ bad username or passwordДЇlags and userdata arenвЂ™t normally used.

3: Connection refused вЂ“ server unavailable.

2: Connection refused вЂ“ invalid client identifier.

1: Connection refused вЂ“ incorrect protocol version.

Note: It is also common to subscribe in the on_connect callback Connection Return Codes Rc (return code) is used for checking that the connection was established.

Print('Bad connection Returned code=',rc) Here is an example function definition: def on_connect(client, userdata, flags, rc): The function should receive 4 parameters, and can be called anything you want. If you want to be sure that the connection attempt was successful then you will need to setup a function to handle this callback before you create the connection. The broker acknowledgement will generate a callback ( on_connect).

When a client issues a connect request to a broker that request should receive an acknowledgment. The connect method is a blocking function which means that your script will stop while the connection is being established. Note: you may need to setup other settings line passwords,last will and testament etc before connecting. This can be the IP address or domain name of the broker. The only parameter you need to provide is the host name. Connect(host, port=1883, keepalive=60, bind_address=вЂќвЂќ)

C program for stop and wait protocol