Dart

Send and Receive WebSocket Frame

See more WebSocket Examples

Demonstrates how to send a websocket text frame to a websocket echo server. This example uses Chilkat's websocket test echo server at ws://websockets.chilkat.io/wsChilkatEcho.ashx

Note: The websockets.chilkat.io server imposes the following limitations:
Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.

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 websockets.chilkat.io
  // IMPORTANT: websockets.chilkat.io accepts frames of up to 16K in size and echoes them back.
  // IMPORTANT: The websockets.chilkat.io server imposes the following limitations: 
  // ---------- Messages must be 16K or less, and each connection is limited to a max of 16 echoed messages.
  rest.connect('websockets.chilkat.io', 80, false, false);
  ws.useConnection(rest);
  ws.addClientHeaders();
  final responseBodyIgnored = rest.fullRequestNoBody('GET', '/wsChilkatEcho.ashx');
  try {
    ws.validateServerHandshake();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // This example demonstrates sending a frame and receiving a text frame.

  // Send a frame containing the string "Hello World!"
  // This will be the first and final frame, and therefore this constitutes the entire message.
  final finalFrame = true;
  try {
    ws.sendFrame('Hello World!', finalFrame);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

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

  // Show the string that was received.
  final receivedStr = ws.getFrameData();
  print('Received: $receivedStr');

  // 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;
  }

  // Should receive the "Close" opcode.
  print('Received opcode: ${ws.frameOpcode}');
  // Should be the same status code we sent (1000)
  print('Received close status code: ${ws.closeStatusCode}');
  // The server may echo the close reason.  If not, this will be empty.
  print('Echoed close reason: ${ws.closeReason}');

  print('Success.');
}