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;

        @Override
        protected long makeKey(Request request) throws IOException {
            return nextKey++;
        }

        @Override
        protected Long peekKey() throws IOException {
            if (recvException != null) {
                throw recvException;
            }
            return peekedKey;
        }

        @Override

         * 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 {

            public U call(DeferredCloser closer, Peeker peeker) throws Exception {
              return function.apply(
                  closer,
                  peeker.getDone(future1),
                  peeker.getDone(future2),
                  peeker.getDone(future3),
                  peeker.getDone(future4),
                  peeker.getDone(future5));
            }

            @Override

                    peeker.getDone(input2Failed);
                    fail("Peeker.getDone() should fail for failed inputs");
                  } catch (ExecutionException expected) {
                  }
                  try {
                    peeker.getDone(nonInput);
                    fail("Peeker should not be able to peek into non-input ClosingFuture.");
                  } catch (IllegalArgumentException expected) {

                    peeker.getDone(input2Failed);
                    fail("Peeker.getDone() should fail for failed inputs");
                  } catch (ExecutionException expected) {
                  }
                  try {
                    peeker.getDone(nonInput);
                    fail("Peeker should not be able to peek into non-input ClosingFuture.");
                  } catch (IllegalArgumentException expected) {

   * a modest limit on `byteCount`, such as 1 MiB.
   */
  @Throws(IOException::class)
  fun peekBody(byteCount: Long): ResponseBody {
    val peeked = body.source().peek()
    val buffer = Buffer()
    peeked.request(byteCount)
    buffer.write(peeked, minOf(byteCount, peeked.buffer.size))
    return buffer.asResponseBody(body.contentType(), buffer.size)
  }

  @JvmName("-deprecated_body")
  @Deprecated(

    while (true) {
      if (peek == null) {
        peek = readToken()
        if (skipCommasAndWhitespace()) break // We peeked a scheme name followed by ','.
        eqCount = skipAll('='.code.toByte())
      }
      if (eqCount == 0) break // We peeked a scheme name.
      if (eqCount > 1) return // Unexpected '=' characters.
      if (skipCommasAndWhitespace()) return // Unexpected ','.