Objective-C

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.

Objective-C

#import <CkoWebSocket.h>
#import <CkoRest.h>
#import <NSString.h>
#import <CkoBinData.h>

BOOL success = NO;

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

CkoWebSocket *ws = [[CkoWebSocket alloc] init];

// 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.

CkoRest *rest = [[CkoRest alloc] init];
// 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" port: [NSNumber numberWithInt: 80] tls: NO autoReconnect: NO];
[ws UseConnection: rest];
[ws AddClientHeaders];
NSString *responseBodyIgnored = [rest FullRequestNoBody: @"GET" uriPath: @"/wsChilkatEcho.ashx"];
success = [ws ValidateServerHandshake];
if (success != YES) {
    NSLog(@"%@",ws.LastErrorText);
    return;
}

// This example sends a small JPG file (about 7KB) in a websocket frame.
CkoBinData *jpgData = [[CkoBinData alloc] init];
success = [jpgData LoadFile: @"qa_data/jpg/starfish.jpg"];

NSLog(@"%@%d",@"Number of bytes to send = ",[jpgData.NumBytes intValue]);

// Send a frame containing the JPG image data.
// This will be the first and final frame, and therefore this constitutes the entire message.
BOOL finalFrame = YES;
success = [ws SendFrameBd: jpgData finalFrame: finalFrame];
if (success != YES) {
    NSLog(@"%@",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.
BOOL receivedFinalFrame = NO;
while (receivedFinalFrame == NO) {

    // 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 != YES) {
        NSLog(@"%@",@"Failed to receive a frame");
        NSLog(@"%@%d",@"ReadFrame fail reason = ",[ws.ReadFrameFailReason intValue]);
        NSLog(@"%@",ws.LastErrorText);
        return;
    }

    receivedFinalFrame = ws.FinalFrame;

    // Show the opcode and final frame bit for the frame just received:
    NSLog(@"%@%@",@"Frame opcode: ",ws.FrameOpcode);
    NSLog(@"%@%d",@"Final frame: ",receivedFinalFrame);
}

// Get the accumulated received data.
CkoBinData *jpgReceivedData = [[CkoBinData alloc] init];
[ws GetFrameDataBd: jpgReceivedData];
NSLog(@"%@%d%@",@"Received ",[jpgReceivedData.NumBytes intValue],@" 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: YES statusCode: [NSNumber numberWithInt: 1000] reason: @"Closing this websocket."];
if (success != YES) {
    NSLog(@"%@",ws.LastErrorText);
    return;
}

// Read the Close response.
success = [ws ReadFrame];
if (success != YES) {
    NSLog(@"%@%d",@"ReadFrame fail reason = ",[ws.ReadFrameFailReason intValue]);
    NSLog(@"%@",ws.LastErrorText);
    return;
}

// Should receive the "Close" opcode.
NSLog(@"%@%@",@"Received opcode: ",ws.FrameOpcode);
// Should be the same status code we sent (1000)
NSLog(@"%@%d",@"Received close status code: ",[ws.CloseStatusCode intValue]);
// The server may echo the close reason.  If not, this will be empty.
NSLog(@"%@%@",@"Echoed close reason: ",ws.CloseReason);

NSLog(@"%@",@"Success.");