Delphi DLL

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.

Delphi DLL

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

...

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

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 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.
finalFrame := True;
success := CkWebSocket_SendFrame(ws,'Hello World!',finalFrame);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkWebSocket__lastErrorText(ws));
    Exit;
  end;

// Read an incoming frame.
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;

// Show the string that was received.
receivedStr := CkWebSocket__getFrameData(ws);
Memo1.Lines.Add('Received: ' + receivedStr);

// 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);

end;