Question

Now I’m working on Websockets, I’m new in that, I finally can send a message of 126 bytes, but I need send longer messages but when I try the connection is closed automatically, my code is:

    public void sendMessage(Stream stream, string message)
    {
        try
        {
            List<byte> lb = new List<byte>();
            string aux = message;
            bool flagStart = false;
            int size;
            while (message.Length > _maxLengthMessage)
            {
                lb = new List<byte>(); 
                // I cut the mesasge in smaller pieces to send
                message = aux.Substring(0, _maxLengthMessage); 
                aux = aux.Substring(_maxLengthMessage);
                if (!flagStart)
                {
                    // In doc of Websockets i sign this piece: not the end, text
                    lb.Add(0x01);
                    flagStart = !flagStart;
                }
                else
                {
                    // In doc of Websockets i sign this piece: not the end, continuation
                    lb.Add(0x00);
                }
                size = message.Length;

                lb.Add((byte)size);
                lb.AddRange(Encoding.UTF8.GetBytes(message));
                stream.Write(lb.ToArray(), 0, size + 2);             
            }
            lb = new List<byte>();
            if (!flagStart)
            {
                // If is this the only message we mark with: end of message, text
                lb.Add(0x81);
                flagStart = !flagStart;
            }
            else
            {
                //else Is the end of the message but is the continuation frame
                lb.Add(0x80);
            } 
            size = aux.Length;

            lb.Add((byte)size);
            lb.AddRange(Encoding.UTF8.GetBytes(aux));
            //lb.AddRange(Encoding.UTF8.GetBytes(i.ToString()));
            stream.Write(lb.ToArray(), 0, size+2);

        }
        catch (Exception ex)
        {
            throw ex;
        }

    }

Some answers say “Go to the The WebSocket protocol”, but it didn’t work for me.

Answer 1

Your code to write the message length needs to be extended. The extended payload in the data framing diagram of the protocol spec shows what’s missing.

For messages up to 125 bytes, your code is correct.

For messages > 125 but <= 65536 bytes, you need to write 3 bytes – the first byte is 126; the following 2 bytes give the message length.

For messages > 65536 bytes, you need to write 9 bytes – the first byte is 127; the following 8 bytes give the message length.