Pascal (Lazarus/Delphi)

Subscribe to Multiple Bitfinex Tickers on One Connection

See more WebSocket Examples

Subscribes to multiple ticker symbols on the public Bitfinex websocket ticker channel and receives ticker updates. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Rest,
  Chilkat.WebSocket,
  Chilkat.JsonObject;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  ws: TWebSocket;
  rest: TRest;
  responseBody: string;
  json1: TJsonObject;
  finalFrame: Boolean;
  json2: TJsonObject;
  receivedFinalFrame: Boolean;
  numUpdatesReceived: Integer;
  receivedText: string;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  ws := TWebSocket.Create;

  //  For brevity, this example does not check for errors when etablishing the WebSocket connection.
  //  See Establish WebSocket Connection for more complete sample code for making the connection.

  rest := TRest.Create;

  //  Connect to api.bitfinex.com
  success := rest.Connect('api.bitfinex.com',443,True,False);
  ws.UseConnection(rest);
  ws.AddClientHeaders();

  responseBody := rest.FullRequestNoBody('GET','/ws');
  success := ws.ValidateServerHandshake();
  if (success <> True) then
    begin
      WriteLn(ws.LastErrorText);
      WriteLn(responseBody);
      WriteLn(rest.ResponseHeader);
      Exit;
    end;

  //  After connecting, the bitfinex websocket server will send
  //  an info message that contains the actual version of the websocket stream.
  //  Receive that message..
  success := ws.ReadFrame();
  if (success <> True) then
    begin
      WriteLn('Failed to receive a frame');
      WriteLn('ReadFrame fail reason = ' + ws.ReadFrameFailReason);
      WriteLn(ws.LastErrorText);
      Exit;
    end;

  //  We should get this:
  //  {"event":"info","version":1.1,"platform":{"status":1}}
  WriteLn(ws.GetFrameData());

  //  Subscribe to the BTCUSD ticker feed.
  //  See https://docs.bitfinex.com/docs for more information.
  json1 := TJsonObject.Create;
  json1.AppendString('event','subscribe');
  json1.AppendString('channel','ticker');
  json1.AppendString('pair','BTCUSD');

  finalFrame := True;
  success := ws.SendFrame(json1.Emit(),finalFrame);

  //  Subscribe to the ETHUSD ticker feed.
  json2 := TJsonObject.Create;
  json2.AppendString('event','subscribe');
  json2.AppendString('channel','ticker');
  json2.AppendString('pair','ETHUSD');

  success := ws.SendFrame(json2.Emit(),finalFrame);

  //  Begin reading the ticker feed.
  //  / This will include a single confirmation response for each subscription.

  //  We'll just read the 1st 5 updates and then exit..
  receivedFinalFrame := False;
  numUpdatesReceived := 0;
  while numUpdatesReceived < 7 do
    begin

      success := ws.ReadFrame();
      if (success <> True) then
        begin
          WriteLn('Failed to receive a frame');
          WriteLn('ReadFrame fail reason = ' + ws.ReadFrameFailReason);
          WriteLn(ws.LastErrorText);
          Exit;
        end;

      //  The responses we desire are in Text frames, where the opcode = 1.
      if (ws.FrameOpcodeInt = 1) then
        begin
          receivedText := ws.GetFrameData();
          WriteLn(receivedText);
          //  Should receive a line of text such as this:
          //  [2751,7349,36.34269559,7349.1,41.01777063,-116.2,-0.0156,7349.1,22188.26055319,7560,7270.5]
          //  Initially, a single confirmation response for each subscription would be received, such as this:
          //  {"event":"subscribed","channel":"ticker","chanId":810,"pair":"BTCUSD"}
          numUpdatesReceived := numUpdatesReceived + 1;
        end;

    end;

  //  This is sample output:
  //  You can see that the 1st message received is the subscription confirmation for the BTCUSD subscribe request.
  //  The next message is a BTCUSD ticker update.
  //  The next message is the confirmation for the ETHUSD subscription.
  //  The next message is an ETHUSD update.
  //  The BTCUSD channel ID is "537", and the ETHUSD channel ID is "700".  The channel IDs are provided in the 
  //  subscription confirmation messages.  Each ticker update begins with the channel ID..

  //  {"event":"subscribed","channel":"ticker","chanId":537,"pair":"BTCUSD"}
  //  [537,6457.9,79.59102302,6458,22.49395741,-24.1,-0.0037,6457.9,13644.52820029,6540,6370.76958739]
  //  {"event":"subscribed","channel":"ticker","chanId":700,"pair":"ETHUSD"}
  //  [700,496.9,247.24493326,496.92,284.09636979,-2.47,-0.0049,496.9,74154.05945261,502.85,486.96]
  //  [537,"hb"]
  //  [700,"hb"]
  //  [700,496.92,233.34338276,496.93,431.78867277,-2.45,-0.0049,496.92,74167.99173586,502.85,486.96]

  //  Close the websocket connection.
  success := ws.SendClose(True,1000,'Closing this websocket.');
  if (success <> True) then
    begin
      WriteLn(ws.LastErrorText);
      Exit;
    end;

  //  Read the Close response.
  success := ws.ReadFrame();
  if (success <> True) then
    begin
      WriteLn('ReadFrame fail reason = ' + ws.ReadFrameFailReason);
      WriteLn(ws.LastErrorText);
      Exit;
    end;

  WriteLn('Success.');


  ws.Free;
  rest.Free;
  json1.Free;
  json2.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.