(Delphi DLL) Subscribe to Multiple Bitfinex Tickers on One Connection

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

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX 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
ws: HCkWebSocket;
rest: HCkRest;
success: Boolean;
responseBody: PWideChar;
json1: HCkJsonObject;
finalFrame: Boolean;
json2: HCkJsonObject;
receivedFinalFrame: Boolean;
numUpdatesReceived: Integer;
receivedText: PWideChar;

begin
//  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 BTCUSD ticker feed.
//  See https://docs.bitfinex.com/docs for more information.
json1 := CkJsonObject_Create();
CkJsonObject_AppendString(json1,'event','subscribe');
CkJsonObject_AppendString(json1,'channel','ticker');
CkJsonObject_AppendString(json1,'pair','BTCUSD');

finalFrame := True;
success := CkWebSocket_SendFrame(ws,CkJsonObject__emit(json1),finalFrame);

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

success := CkWebSocket_SendFrame(ws,CkJsonObject__emit(json2),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 := 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]
        //  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 := 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(json1);
CkJsonObject_Dispose(json2);

end;