synchronized (this.inLock) {
                    final Long peekKey = peekKey();
                    if (peekKey == firstKey) {
                        doRecv(response);
                        response.received();
                        return response;
                    }
                    doSkip(peekKey);
                }
            }

     * Reads and returns the key of the next message without consuming it.
     *
     * @return the request key of the next message
     * @throws IOException if an I/O error occurs
     */
    protected abstract Request peekKey() throws IOException;

    /**
     * Sends a request to the remote endpoint.
     *
     * @param request the request to send
     * @throws IOException if an I/O error occurs
     */

            out.write(sbuf, 0, 4 + n);
            out.flush();
            /* Note the Transport thread isn't running yet so we can
             * read from the socket here.
             */
            if (peekKey() == null) { /* try to read header */
                throw new IOException("transport closed in negotiate");
            }
            final int size = Encdec.dec_uint16be(sbuf, 2) & 0xFFFF;

         * read from the socket here.
         */
        try {
            this.socket.setSoTimeout(this.transportContext.getConfig().getConnTimeout());
            if (peekKey() == null) { /* try to read header */
                throw new IOException("transport closed in negotiate");
            }
        } finally {

     * Gets the length of the first message in the pipe
     * @return the messageLength
     */
    public int getMessageLength() {
        return this.messageLength;
    }

    /**
     * Gets the data peeked from the pipe
     * @return the data
     */
    public byte[] getData() {
        return this.data;
    }

    /**
     * {@inheritDoc}
     *
     * @see Decodable#decode(byte[], int, int)
     */