Delphi DLL

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.

Delphi DLL

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
ws: HCkWebSocket;
rest: HCkRest;
responseBodyIgnored: PWideChar;
jpgData: HCkBinData;
finalFrame: Boolean;
receivedFinalFrame: Boolean;
jpgReceivedData: HCkBinData;

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 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 := CkRest_Connect(rest,'websockets.chilkat.io',80,False,False);
CkWebSocket_UseConnection(ws,rest);
CkWebSocket_AddClientHeaders(ws);
responseBodyIgnored := CkRest__fullRequestNoBody(rest,'GET','/wsChilkatEcho.ashx');
success := CkWebSocket_ValidateServerHandshake(ws);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
    Exit;
  end;

// This example sends a small JPG file (about 7KB) in a websocket frame.
jpgData := CkBinData_Create();
success := CkBinData_LoadFile(jpgData,'qa_data/jpg/starfish.jpg');

Memo1.Lines.Add('Number of bytes to send = ' + IntToStr(CkBinData_getNumBytes(jpgData)));

// Send a frame containing the JPG image data.
// This will be the first and final frame, and therefore this constitutes the entire message.
finalFrame := True;
success := CkWebSocket_SendFrameBd(ws,jpgData,finalFrame);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
    Exit;
  end;

// 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.
receivedFinalFrame := False;
while receivedFinalFrame = False do
  begin

    // 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 := 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;

    receivedFinalFrame := CkWebSocket_getFinalFrame(ws);

    // Show the opcode and final frame bit for the frame just received:
    Memo1.Lines.Add('Frame opcode: ' + CkWebSocket__frameOpcode(ws));
    Memo1.Lines.Add('Final frame: ' + IntToStr(Ord(receivedFinalFrame)));
  end;

// Get the accumulated received data.
jpgReceivedData := CkBinData_Create();
CkWebSocket_GetFrameDataBd(ws,jpgReceivedData);
Memo1.Lines.Add('Received ' + IntToStr(CkBinData_getNumBytes(jpgReceivedData)) + ' bytes');

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

// 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;

// Should receive the "Close" opcode.
Memo1.Lines.Add('Received opcode: ' + CkWebSocket__frameOpcode(ws));
// Should be the same status code we sent (1000)
Memo1.Lines.Add('Received close status code: ' + IntToStr(CkWebSocket_getCloseStatusCode(ws)));
// The server may echo the close reason.  If not, this will be empty.
Memo1.Lines.Add('Echoed close reason: ' + CkWebSocket__closeReason(ws));

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

CkWebSocket_Dispose(ws);
CkRest_Dispose(rest);
CkBinData_Dispose(jpgData);
CkBinData_Dispose(jpgReceivedData);

end;