(Delphi ActiveX) Read Bitfinex WebSocket Ticker Channel

Subscribes to the public Bitfinex websocket ticker channel and receives ticker updates.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
ws: TChilkatWebSocket;
rest: TChilkatRest;
success: Integer;
responseBody: WideString;
json: TChilkatJsonObject;
finalFrame: Integer;
receivedFinalFrame: Integer;
numUpdatesReceived: Integer;
receivedText: WideString;

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

ws := TChilkatWebSocket.Create(Self);

// 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 := TChilkatRest.Create(Self);

// Connect to api.bitfinex.com
success := rest.Connect('api.bitfinex.com',443,1,0);
ws.UseConnection(rest.ControlInterface);
ws.AddClientHeaders();

responseBody := rest.FullRequestNoBody('GET','/ws');
success := ws.ValidateServerHandshake();
if (success <> 1) then
  begin
    Memo1.Lines.Add(ws.LastErrorText);
    Memo1.Lines.Add(responseBody);
    Memo1.Lines.Add(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 <> 1) then
  begin
    Memo1.Lines.Add('Failed to receive a frame');
    Memo1.Lines.Add('ReadFrame fail reason = ' + IntToStr(ws.ReadFrameFailReason));
    Memo1.Lines.Add(ws.LastErrorText);
    Exit;
  end;

// We should get this:
// {"event":"info","version":1.1,"platform":{"status":1}}
Memo1.Lines.Add(ws.GetFrameData());

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

finalFrame := 1;
success := ws.SendFrame(json.Emit(),finalFrame);

// Read the response.
success := ws.ReadFrame();
if (success <> 1) then
  begin
    Memo1.Lines.Add('Failed to receive a frame');
    Memo1.Lines.Add('ReadFrame fail reason = ' + IntToStr(ws.ReadFrameFailReason));
    Memo1.Lines.Add(ws.LastErrorText);
    Exit;
  end;

// Examine the response
// We should get this:
// {"event":"subscribed","channel":"ticker","chanId":2751,"pair":"BTCUSD"}
Memo1.Lines.Add(ws.GetFrameData());

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

    success := ws.ReadFrame();
    if (success <> 1) then
      begin
        Memo1.Lines.Add('Failed to receive a frame');
        Memo1.Lines.Add('ReadFrame fail reason = ' + IntToStr(ws.ReadFrameFailReason));
        Memo1.Lines.Add(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();
        Memo1.Lines.Add(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]
        numUpdatesReceived := numUpdatesReceived + 1;
      end;

  end;

// Close the websocket connection.
success := ws.SendClose(1,1000,'Closing this websocket.');
if (success <> 1) then
  begin
    Memo1.Lines.Add(ws.LastErrorText);
    Exit;
  end;

// Read the Close response.
success := ws.ReadFrame();
if (success <> 1) then
  begin
    Memo1.Lines.Add('ReadFrame fail reason = ' + IntToStr(ws.ReadFrameFailReason));
    Memo1.Lines.Add(ws.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Success.');
end;