Java

WebSocket Send/Receive Binary Data

See more WebSocket Examples

Demonstrates how to send and receive binary data on a websocket. 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.

Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

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

    CkWebSocket ws = new 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.

    CkRest rest = new 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.
    success = rest.Connect("websockets.chilkat.io",80,false,false);
    ws.UseConnection(rest);
    ws.AddClientHeaders();
    String responseBodyIgnored = rest.fullRequestNoBody("GET","/wsChilkatEcho.ashx");
    success = ws.ValidateServerHandshake();
    if (success != true) {
        System.out.println(ws.lastErrorText());
        return;
        }

    // This example sends a small JPG file (about 7KB) in a websocket frame.
    CkBinData jpgData = new CkBinData();
    success = jpgData.LoadFile("qa_data/jpg/starfish.jpg");

    System.out.println("Number of bytes to send = " + jpgData.get_NumBytes());

    // Send a frame containing the JPG image data.
    // This will be the first and final frame, and therefore this constitutes the entire message.
    boolean finalFrame = true;
    success = ws.SendFrameBd(jpgData,finalFrame);
    if (success != true) {
        System.out.println(ws.lastErrorText());
        return;
        }

    // Read the echoed binary frame(s).
    // (We sent the JPG file in a single frame, but we may receive the echo in multiple frames, but it will be one message.)
    // Read an incoming frames until we receive the final frame.
    boolean receivedFinalFrame = false;
    while (receivedFinalFrame == false) {

        // The ws object is accumulating the received data internally.  Once we get the final frame, we'll get the 
        // accumulated data which should constitute the entire JPG.
        success = ws.ReadFrame();
        if (success != true) {
            System.out.println("Failed to receive a frame");
            System.out.println("ReadFrame fail reason = " + ws.get_ReadFrameFailReason());
            System.out.println(ws.lastErrorText());
            return;
            }

        receivedFinalFrame = ws.get_FinalFrame();

        // Show the opcode and final frame bit for the frame just received:
        System.out.println("Frame opcode: " + ws.frameOpcode());
        System.out.println("Final frame: " + receivedFinalFrame);
        }

    // Get the accumulated received data.
    CkBinData jpgReceivedData = new CkBinData();
    ws.GetFrameDataBd(jpgReceivedData);
    System.out.println("Received " + jpgReceivedData.get_NumBytes() + " bytes");

    // Save the received JPG to a file so we can check it..
    jpgReceivedData.WriteFile("qa_output/starfish_ws.jpg");

    // Close the websocket connection.
    success = ws.SendClose(true,1000,"Closing this websocket.");
    if (success != true) {
        System.out.println(ws.lastErrorText());
        return;
        }

    // Read the Close response.
    success = ws.ReadFrame();
    if (success != true) {
        System.out.println("ReadFrame fail reason = " + ws.get_ReadFrameFailReason());
        System.out.println(ws.lastErrorText());
        return;
        }

    // Should receive the "Close" opcode.
    System.out.println("Received opcode: " + ws.frameOpcode());
    // Should be the same status code we sent (1000)
    System.out.println("Received close status code: " + ws.get_CloseStatusCode());
    // The server may echo the close reason.  If not, this will be empty.
    System.out.println("Echoed close reason: " + ws.closeReason());

    System.out.println("Success.");
  }
}