Function sendWebSocketFrame

src/Server/WebTerminalRequestHandler.cpp:85–118

Send a WebSocket frame. Server-to-client frames are not masked. Header and payload are combined into a single buffer to avoid partial frame writes.

/// Send a WebSocket frame. Server-to-client frames are not masked.
/// Header and payload are combined into a single buffer to avoid partial frame writes.
void sendWebSocketFrame(Poco::Net::StreamSocket & socket, uint8_t opcode, const char * data, size_t len)
{
    uint8_t header[10];
    size_t header_len = 2;

    header[0] = 0x80 | opcode; /// FIN + opcode

    if (len < 126)
    {
        header[1] = static_cast<uint8_t>(len);
    }
    else if (len < 65536)
    {
        header[1] = 126;
        header[2] = static_cast<uint8_t>((len >> 8) & 0xFF);
        header[3] = static_cast<uint8_t>(len & 0xFF);
        header_len = 4;
    }
    else
    {
        header[1] = 127;
        for (int i = 0; i < 8; ++i)
            header[2 + i] = static_cast<uint8_t>((len >> (56 - 8 * i)) & 0xFF);
        header_len = 10;
    }

    /// Combine header and payload into a single send to avoid partial frame writes
    String buf;
    buf.reserve(header_len + len);
    buf.append(reinterpret_cast<const char *>(header), header_len);
    if (len > 0)
        buf.append(data, len);
    sendAllBytes(socket, buf.data(), buf.size());
}

void sendWebSocketBinary(Poco::Net::StreamSocket & socket, const char * data, size_t len)
{