net.corda.core.messaging / TopicSession / <init>

# <init>

`TopicSession(topic: String, sessionID: Long = DEFAULT_SESSION_ID)`

An identifier for the endpoint MessagingService message handlers listen at.

### Parameters

`topic` - identifier for the general subject of the message, for example "platform.network_map.fetch". The topic can be the empty string to match all messages (session ID must be DEFAULT_SESSION_ID).
`sessionID` - identifier for the session the message is part of. For services listening before a session is established, use DEFAULT_SESSION_ID.