A protocol identifier is specified when creating a atk.Socket, which is a family/type specific identifier, where 0 means the default protocol for the particular family/type.
This enum contains a set of commonly available and used protocols. You can also pass any other identifiers handled by the platform in order to use protocols not listed here.
The protocol type is unknown
The default protocol for the family/type
TCP over IP
UDP over IP
SCTP over IP