Delphi TURN Server Component (3/4)

Basic Usage 

Usually TURN servers runs on UDP port 3478 and require Long-Term credentials, so in order to configure a TURN server, set the listening port (by default 3478) and start the server.

Configure the server

• Port: the listening Server port, example: 3478
• Define the Long-Term Credentials properties in TURNOptions.Authentication.LongTermCredentials
• Handle the OnSTUNRequestAuthorization to set the password when a TURN client sends a request to TURN Server.

Set the property Active = True to start the STUN server.

oTURN := TsgcTURNServer.Create(nil);
oTURN.Port := 3478;
oTURN.TURNOptions.Authentication.Enabled := True;
oTURN.TURNOptions.Authentication.LongTermCredentials.Enabled := True;
oTURN.TURNOptions.Authentication.LongTermCredentials.Realm := 'esegece.com';
oTURN.Active := True;


procedure OnSTUNRequestAuthorization(Sender: TObject; const aRequest: TsgcSTUN_Message; const aUsername, aRealm: string; var Password: string);
begin
  if (aUsername = 'user') and (aRealm = 'esegece.com') then
    Password := 'password';
end; 

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;