Delphi DLL

Read Bitfinex WebSocket Ticker Channel

See more WebSocket Examples

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

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
ws: HCkWebSocket;
rest: HCkRest;
responseBody: PWideChar;
json: HCkJsonObject;
finalFrame: Boolean;
receivedFinalFrame: Boolean;
numUpdatesReceived: Integer;
receivedText: PWideChar;

begin
success := False;

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

ws := CkWebSocket_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 := CkRest_Create();

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

responseBody := CkRest__fullRequestNoBody(rest,'GET','/ws');
success := CkWebSocket_ValidateServerHandshake(ws);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
    Memo1.Lines.Add(responseBody);
    Memo1.Lines.Add(CkRest__responseHeader(rest));
    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 := CkWebSocket_ReadFrame(ws);
if (success <> True) then
  begin
    Memo1.Lines.Add('Failed to receive a frame');
    Memo1.Lines.Add('ReadFrame fail reason = ' + IntToStr(CkWebSocket_getReadFrameFailReason(ws)));
    Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
    Exit;
  end;

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

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

finalFrame := True;
success := CkWebSocket_SendFrame(ws,CkJsonObject__emit(json),finalFrame);

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

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

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

    success := CkWebSocket_ReadFrame(ws);
    if (success <> True) then
      begin
        Memo1.Lines.Add('Failed to receive a frame');
        Memo1.Lines.Add('ReadFrame fail reason = ' + IntToStr(CkWebSocket_getReadFrameFailReason(ws)));
        Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
        Exit;
      end;

    // The responses we desire are in Text frames, where the opcode = 1.
    if (CkWebSocket_getFrameOpcodeInt(ws) = 1) then
      begin
        receivedText := CkWebSocket__getFrameData(ws);
        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 := CkWebSocket_SendClose(ws,True,1000,'Closing this websocket.');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
    Exit;
  end;

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

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

CkWebSocket_Dispose(ws);
CkRest_Dispose(rest);
CkJsonObject_Dispose(json);

end;