The server runs indefinitely, but can be stopped by a keyboard interrrupt.
The executor to be hosted by the server.
The number of network threads to use for handling gRPC calls.
The port to listen on (for gRPC), must be a non-zero integer.
The optional credentials to use for the secure connection if
any, or None if the server should open an insecure port. If specified,
must be a valid ServerCredentials object that can be accepted by the
gRPC server's add_secure_port().
The optional list of server options, each in the (key, value)
format accepted by the grpc.server() constructor.