## Callback interface

The callback interface of the transport module contains several functions. Some of which are mandatory while others are only optional:

send_message - Send a message. Mandatory

block - Block the transport. Optional

This function is usefull for flow control.

unblock - Unblock the transport. Optional

For more detail, see the megaco_transport behaviour definition.

## Examples

The Megaco/H.248 application contains implementations for the two protocols specified by the Megaco/H.248 standard; UDP, see megaco_udp, and TCP/TPKT, see megaco_tcp.