Basic ALH access

The following classes provide basic access to the resources on sensor nodes available through the ALH protocol.

ALH protocol implementations

class vesna.alh.ALHTerminal(f)

ALH protocol implementation through a serial terminal.

This implementation is used for testing and debugging when a sensor node is connected directly to a computer over a serial line.

Parameters:f – path to the character device of the terminal (usually an instance of the serial.Serial class)
get(*args, **kwargs)

Issue a GET request to the service.

Raises an ALHException in case of an error.

Parameters:
  • resource – resource to issue request to
  • args – arbitrary string arguments for the request
Returns:

vesna.alh.ALHResponse object
post(*args, **kwargs)

Issue a POST request to the service

Raises an ALHException in case of an error.

Parameters:
  • resource – resource to issue request to
  • data – POST data to attach to the request
  • args – arbitrary string arguments for the request
Returns:

vesna.alh.ALHResponse object
class vesna.alh.ALHWeb(base_url, cluster_id)

ALH protocol implementation through the HTTP infrastructure server.

ALHWeb is typically used to access the coordinator of a ZigBee mesh network.

If the API end-point is using basic authentication, you will be prompted for credentials on the command line.

You can also save credentials into either a file named .alhrc in your home directory or alhrc in the current directory. Format of the file is as in the following example:

Host example.com
User <username>
Password <password>
# more Host, User, Password lines can follow
Parameters:
  • base_url – base URL of the HTTP API (e.g. https://crn.log-a-tec.eu/communicator)
  • cluster_id – numerical cluster id
get(*args, **kwargs)

Issue a GET request to the service.

Raises an ALHException in case of an error.

Parameters:
  • resource – resource to issue request to
  • args – arbitrary string arguments for the request
Returns:

vesna.alh.ALHResponse object
post(*args, **kwargs)

Issue a POST request to the service

Raises an ALHException in case of an error.

Parameters:
  • resource – resource to issue request to
  • data – POST data to attach to the request
  • args – arbitrary string arguments for the request
Returns:

vesna.alh.ALHResponse object
class vesna.alh.ALHProxy(alhproxy, addr)

ALH protocol implementation through an ALH proxy.

This implementation forwards arbitrary ALH requests through the “nodes” resource on an ALH service used as a proxy.

ALHProxy is typically used to access nodes on the ZigBee mesh network behind the coordinator.

Parameters:
  • alhproxy – ALH implementation used as a proxy
  • addr – ZigBee address of the node to forward requests to
get(*args, **kwargs)

Issue a GET request to the service.

Raises an ALHException in case of an error.

Parameters:
  • resource – resource to issue request to
  • args – arbitrary string arguments for the request
Returns:

vesna.alh.ALHResponse object
post(*args, **kwargs)

Issue a POST request to the service

Raises an ALHException in case of an error.

Parameters:
  • resource – resource to issue request to
  • data – POST data to attach to the request
  • args – arbitrary string arguments for the request
Returns:

vesna.alh.ALHResponse object

Response class

class vesna.alh.ALHResponse(content)

This class represents the response of a resource handler.

The ALH protocol does not define the encoding of strings passed thorugh it. It can be used for binary data as well. In practice however, most strings are 7-bit ASCII. Hence this class provides ASCII-decoded form of the response for convenience, as well as the undecoded binary.

text

Text form of the response (ASCII).

content

Binary form of the response (bytes object on Python 3).

Exception classes

class vesna.alh.ALHException

Base class for errors related to the ALH protocol