For messages received on connections, this is the user data
associated with the connection.
This is *usually* the same as calling GetConnection() and then
fetching the user data associated with that connection, but for
the following subtle differences:
- This user data will match the connection's user data at the time
is captured at the time the message is returned by the API.
If you subsequently change the userdata on the connection,
this won't be updated.
- This is an inline call, so it's *much* faster.
- You might have closed the connection, so fetching the user data
would not be possible.
For messages received on connections, this is the user data associated with the connection.
This is *usually* the same as calling GetConnection() and then fetching the user data associated with that connection, but for the following subtle differences:
- This user data will match the connection's user data at the time is captured at the time the message is returned by the API. If you subsequently change the userdata on the connection, this won't be updated. - This is an inline call, so it's *much* faster. - You might have closed the connection, so fetching the user data would not be possible.
Not used when sending messages.