Zig

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.

Zig

const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

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

    const ws = try chilkat.WebSocket.init();
    defer ws.deinit();

    // 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.

    const rest = try chilkat.Rest.init();
    defer rest.deinit();
    // 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.
    try rest.connect("websockets.chilkat.io", 80, false, false);
    ws.useConnection(rest) catch {};
    ws.addClientHeaders() catch {};
    _ = try rest.fullRequestNoBody(alloc, "GET", "/wsChilkatEcho.ashx");
    ws.validateServerHandshake() catch {
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        return;
    };

    // This example sends a small JPG file (about 7KB) in a websocket frame.
    const jpg_data = try chilkat.BinData.init();
    defer jpg_data.deinit();
    try jpg_data.loadFile("qa_data/jpg/starfish.jpg");

    std.debug.print("Number of bytes to send = {d}\n", .{jpg_data.getNumBytes()});

    // Send a frame containing the JPG image data.
    // This will be the first and final frame, and therefore this constitutes the entire message.
    const final_frame = true;
    ws.sendFrameBd(jpg_data, final_frame) catch {
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        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.
    var received_final_frame: bool = false;
    while (!received_final_frame) {
        // 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.
        ws.readFrame() catch {
            std.debug.print("Failed to receive a frame\n", .{});
            std.debug.print("ReadFrame fail reason = {d}\n", .{ws.getReadFrameFailReason()});
            std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
            return;
        };

        received_final_frame = ws.getFinalFrame();

        // Show the opcode and final frame bit for the frame just received:
        std.debug.print("Frame opcode: {s}\n", .{try ws.getFrameOpcode(alloc)});
        std.debug.print("Final frame: {}\n", .{received_final_frame});
    }

    // Get the accumulated received data.
    const jpg_received_data = try chilkat.BinData.init();
    defer jpg_received_data.deinit();
    ws.getFrameDataBd(jpg_received_data) catch {};
    std.debug.print("Received {d} bytes\n", .{jpg_received_data.getNumBytes()});

    // Save the received JPG to a file so we can check it..
    jpg_received_data.writeFile("qa_output/starfish_ws.jpg") catch {};

    // Close the websocket connection.
    ws.sendClose(true, 1000, "Closing this websocket.") catch {
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        return;
    };

    // Read the Close response.
    ws.readFrame() catch {
        std.debug.print("ReadFrame fail reason = {d}\n", .{ws.getReadFrameFailReason()});
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        return;
    };

    // Should receive the "Close" opcode.
    std.debug.print("Received opcode: {s}\n", .{try ws.getFrameOpcode(alloc)});
    // Should be the same status code we sent (1000)
    std.debug.print("Received close status code: {d}\n", .{ws.getCloseStatusCode()});
    // The server may echo the close reason.  If not, this will be empty.
    std.debug.print("Echoed close reason: {s}\n", .{try ws.getCloseReason(alloc)});

    std.debug.print("Success.\n", .{});
}