TURN Server | Allocations

All TURN operations revolve around allocations and all TURN messages are associated with an Allocation. An allocation consists of:

 

• The relayed transport address
• The 5-Tuple: client's IP Address, client's IP port, server IP address, server port and transport protocol.
• The authentication information.
• The time-to-expiry for each relayed transport address.
• A list of permissions for each relayed transport address.
• A list of channels bindings for each relayed transport address.

 

When a TURN client sends an Allocate request, this TURN message is processed by server and tries to create a new Relayed Transport Address. By default, if there is any available UDP port, it will create a new Relayed Address, but you can use OnTURNBeforeAllocate event to reject a new Allocation request.

 

procedure OnTURNBeforeAllocate(Sender: TObject; const aSocket: TsgcSocketConnection; 
  const aIP: string; aPort: Word; var Reject: Boolean);
begin
  if not (your own rules) then
	Reject := false;
end;

If the process continues, the server creates a new allocation and the event OnTURNCreateAllocation is called. This event provides information about the Allocation through the class TsgcTURNAllocationItem.

 

procedure OnTURNCreateAllocation(Sender: TObject; const aSocket: TsgcSocketConnection; 
  const Allocation: TsgcTURNAllocationItem);
begin
  DoLog('New Allocation: ' + Allocation.RelayIP + ':' + IntToStr(Allocation.RelayPort));
end;

 

When the Allocation expires or is deleted receiving a Refresh Request from client with a lifetime of zero, the event OnTURNDeleteAllocation event is fired.

 

procedure OnTURNDeleteAllocation(Sender: TObject; const aSocket: TsgcSocketConnection; 
  const Allocation: TsgcTURNAllocationItem);
begin
  DoLog('Allocation Deleted: ' + Allocation.RelayIP + ':' + IntToStr(Allocation.RelayPort));
end;