Duplex transport

A duplex transport is an abstraction that provides duplex communications between a client and server. TCP is the primary duplex transport provided by IceRPC.

The duplex transport abstraction allows writing custom duplex transports. For example, the RFCOMM transport could be supported by implementing this abstraction. Such custom transports need to conform to a number of requirements which are documented on this page.

IceRPC uses duplex transports for the implementation of the ice protocol and the implementation of the Slic transport.

The duplex transport requirements

IceRPC requires a duplex transport to be connection-oriented and to support the following features:

• full-duplex communication over a bidirectional byte stream
• flow control
• half-closure where each side of the connection can be closed independently
• graceful closure to allow closing the connection once all the data is delivered
• abortive closure to close the connection and release its resources immediately without waiting for the data to be delivered

Duplex transport and TLS

The TLS configuration from the application is passed through the duplex transport abstraction to allow the transport implementation to setup TLS for duplex connections.

A transport is free to only support non-secure connections, only support secure connections or support both. For example, the TCP duplex transport can create secure or non-secure connections.

If the application provides TLS configuration, the transport must create secure connections. If it doesn't support TLS, it must fail.

See also Security with TLS for additional information.

The C# duplex transport abstraction

The C# duplex transport abstraction is composed of a number of interfaces that a custom transport needs to implement:

• IDuplexClientTransport: a factory to create outgoing connections
• IDuplexServerTransport: a factory to create listeners
• IListener<IDuplexConnection>: a factory to listen for and create incoming connections
• IDuplexConnection: a connection to allow a client and server to communicate

The API documentation of these interfaces specifies the contract a custom transport needs to comply with.

To use a custom transport, the application needs to provide an instance of IDuplexServerTransport or IDuplexClientTransport to the Server, ConnectionCache or ClientConnection constructors.