TCP transport keep-alive messages

[ecorm]

TCP transports should optionally make use of the RawSocket transport-level PING messages to help keep long-lived connections open. The ping interval should be configurable by the user.

[ecorm]

Asked here about the rationale for PING/PONG messages over the SO_KEEPALIVE socket option: wamp-proto/wamp-proto#274 (comment)

[ecorm]

Resolved via e64acc9.