Dart

Subscribe to Multiple Bitfinex Tickers on One Connection

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

import 'package:chilkat/chilkat.dart';

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

  final ws = CkWebSocket();

  // 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.

  final rest = CkRest();

  // Connect to api.bitfinex.com
  rest.connect('api.bitfinex.com', 443, true, false);
  ws.useConnection(rest);
  ws.addClientHeaders();

  final responseBody = rest.fullRequestNoBody('GET', '/ws');
  try {
    ws.validateServerHandshake();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    print(responseBody);
    print(rest.responseHeader);
    return;
  }

  // After connecting, the bitfinex websocket server will send
  // an info message that contains the actual version of the websocket stream.
  // Receive that message..
  try {
    ws.readFrame();
  } on ChilkatException catch (e) {
    print('Failed to receive a frame');
    print('ReadFrame fail reason = ${ws.readFrameFailReason}');
    print(e.lastErrorText);
    return;
  }

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

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

  final finalFrame = true;
  ws.sendFrame(json1.emit(), finalFrame);

  // Subscribe to the ETHUSD ticker feed.
  final json2 = CkJsonObject();
  json2.appendString('event', 'subscribe');
  json2.appendString('channel', 'ticker');
  json2.appendString('pair', 'ETHUSD');

  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..
  var numUpdatesReceived = 0;
  while (numUpdatesReceived < 7) {

    try {
      ws.readFrame();
    } on ChilkatException catch (e) {
      print('Failed to receive a frame');
      print('ReadFrame fail reason = ${ws.readFrameFailReason}');
      print(e.lastErrorText);
      return;
    }

    // The responses we desire are in Text frames, where the opcode = 1.
    if (ws.frameOpcodeInt == 1) {
      final receivedText = ws.getFrameData();
      print(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++;
    }
  }

  // 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.
  try {
    ws.sendClose(true, 1000, 'Closing this websocket.');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Read the Close response.
  try {
    ws.readFrame();
  } on ChilkatException catch (e) {
    print('ReadFrame fail reason = ${ws.readFrameFailReason}');
    print(e.lastErrorText);
    return;
  }

  print('Success.');
}