Zig

Send and Receive WebSocket Messages

See more WebSocket Examples

This example how to send and receive websocket messages.

A WebSocket message can be composed of one or more frames. The simple case is where a single frame is both the first and last frame in a message. This is the case where the 1st frame in the message has the "final frame" bit set.

This example demonstrates sending and receiving multi-frame messages.

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 demonstrates sending and receiving a multi-frame message.

    // The websocket message will be composed of three text lines, each frame will contain a single line.

    // Send the 1st frame in the message.
    var final_frame: bool = false;
    ws.sendFrame("This is the 1st frame\r\n", final_frame) catch {
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        return;
    };

    // Send the 2nd frame in the message.
    ws.sendFrame("This is the 2nd frame\r\n", final_frame) catch {
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        return;
    };

    // Send the 3rd and final frame in the message.
    final_frame = true;
    ws.sendFrame("This is the 3rd frame\r\n", final_frame) catch {
        std.debug.print("{s}\n", .{try ws.getLastErrorText(alloc)});
        return;
    };

    // Read an incoming frames until we receive the final frame.
    // Note: It may be that the echo server (websockets.chilkat.io) responds with
    // the full message in a single final frame.
    var received_final_frame: bool = false;
    while (!received_final_frame) {
        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});
    }

    // Return the message accumulated in the above calls to ReadFrame.
    const received_msg = try ws.getFrameData(alloc);
    std.debug.print("Received: {s}\n", .{received_msg});

    // 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", .{});
}