Connection between service and client allowing to pass messages
between them. Connection stays open until client Isolate exits.
When connection is closed, service will be notified to give it
a chance to perform necessary cleanup.
Receives a message. Blocks until there is a message to receive.
On client side, it receives message from service. On service side,
it receives message from client.
received message
Sends a message. Blocks until message is received. On client side,
it sends message to service. On service side, it sends message
to client.
Parameters: msg - message to send