Delphi STUN/TURN Server and Client (4/4)

Build a STUN/TURN Server 

The process to create a STUN/TURN Delphi Server is very simple, just create a TsgcTURNServer and configure the following properties:

• Port: by default it's 3478, the common port for STUN/TURN protocol.
• STUNOptions: here you can configure the STUN Options, usually STUN requests doesn't make use of authentication, so you can leave this with default values.
• TURNOptions. here you can configure the TURN Options, usually TURN servers require Long-Term credentials (because TURN use Relay Address to exchange data between peers behind NATs and this require high resources). Here you can configure the IP Address of the Relayed Address, configure it in TURNOptions.Allocation.RelayIP.

Handle the event OnSTUNRequestAuthorization to set the password when a TURN client sends a Request.

Finally set Active property to True to start the server.

Find below a sample configuration where STUN requests doesn't require authorization and TURN requests require Long-Term credentials.

oTURN := TsgcTURNServer.Create(nil);
oTURN.Port := 3478;
oTURN.STUNOptions.Authentication.Enabled := False;
oTURN.TURNOptions.Authentication.Enabled := True;
oTURN.TURNOptions.Authentication.LongTermCredentials.Enabled := True;
oTURN.TURNOptions.Authentication.LongTermCredentials.Realm := 'sgcWebSockets';
oTURN.TURNOptions.Authentication.LongTermCredentials.StaleNonce := 600;
oTURN.Active := True;


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

Build a STUN/TURN Client 

Create a new Delphi STUN/TURN Client is as simple as a Server. Just create a TsgcTURNClient and configure the following properties:

• Host: is the dns name or IP Address where the STUN/TURN server is running.
• Port: is the port, by default 3478.
• STUNOptions: here you can configure the STUN Options, usually STUN requests doesn't make use of authentication, so you can leave this with default values.
• TURNOptions. here you can configure the TURN Options, usually TURN servers require Long-Term credentials (because TURN use Relay Address to exchange data between peers behind NATs and this require high resources).

Allocate IP Address

TURN Protocol allows to use a Relayed IP Address to exchange data between peers that are behind NATs.

To create a new Relayed IP Address on a TURN server, the client must first call the method Allocate, this method sends a Request to the TURN server to create a new Relayed IP Address, if the TURN server can create a new Relayed IP Address, the client will receive a successful response. The client will be able to communicate with other peers during the time defined in the Allocation's lifetime.

oTURN := TsgcTURNClient.Create(nil);
oTURN.Host := 'turn.sgcwebsockets.com';
oTURN.Port := 3478;
oTURN.Allocate();

procedure OnTURNAllocate(Sender: TObject; const aSocket: TsgcSocketConnection; const
aMessage: TsgcSTUN_Message; const aAllocation: TsgcTURN_ResponseAllocation);
begin
  DoLog('Relayed IP: ' + aAllocation.RelayedIP + '. Relayed Port: ' + IntToStr(aAllocation.RelayedPort));
end;

procedure OnSTUNResponseError(Sender: TObject; const aMessage: TsgcSTUN_Message;
const aError: TsgcSTUN_ResponseError);
begin
  DoLog('Error: ' + IntToStr(aError.Code) + ' ' + aError.Reason);
end; 

The lifetime can be updated to avoid expiration using the method Refresh. The Lifetime is the number of seconds to expire. If the value is zero the Allocation will be deleted.

oTURN.Refresh(600); 

TURN Server 

Compiled TURN Server / Client Demo