/**
   * {@inheritDoc}
   *
   * <p>SCTP input data callback.
   */
  @Override
  public void onSctpPacket(
      byte[] data, int sid, int ssn, int tsn, long ppid, int context, int flags) {
    if (ppid == WEB_RTC_PPID_CTRL) {
      // Channel control PPID
      try {
        onCtrlPacket(data, sid);
      } catch (IOException e) {
        logger.error("IOException when processing ctrl packet", e);
      }
    } else if (ppid == WEB_RTC_PPID_STRING || ppid == WEB_RTC_PPID_BIN) {
      WebRtcDataStream channel;

      synchronized (this) {
        channel = channels.get(sid);
      }

      if (channel == null) {
        logger.error("No channel found for sid: " + sid);
        return;
      }
      if (ppid == WEB_RTC_PPID_STRING) {
        // WebRTC String
        String str;
        String charsetName = "UTF-8";

        try {
          str = new String(data, charsetName);
        } catch (UnsupportedEncodingException uee) {
          logger.error("Unsupported charset encoding/name " + charsetName, uee);
          str = null;
        }
        channel.onStringMsg(str);
      } else {
        // WebRTC Binary
        channel.onBinaryMsg(data);
      }
    } else {
      logger.warn("Got message on unsupported PPID: " + ppid);
    }
  }
  /**
   * Handles control packet.
   *
   * @param data raw packet data that arrived on control PPID.
   * @param sid SCTP stream id on which the data has arrived.
   */
  private synchronized void onCtrlPacket(byte[] data, int sid) throws IOException {
    ByteBuffer buffer = ByteBuffer.wrap(data);
    int messageType = /* 1 byte unsigned integer */ 0xFF & buffer.get();

    if (messageType == MSG_CHANNEL_ACK) {
      if (logger.isDebugEnabled()) {
        logger.debug(getEndpoint().getID() + " ACK received SID: " + sid);
      }
      // Open channel ACK
      WebRtcDataStream channel = channels.get(sid);
      if (channel != null) {
        // Ack check prevents from firing multiple notifications
        // if we get more than one ACKs (by mistake/bug).
        if (!channel.isAcknowledged()) {
          channel.ackReceived();
          notifyChannelOpened(channel);
        } else {
          logger.warn("Redundant ACK received for SID: " + sid);
        }
      } else {
        logger.error("No channel exists on sid: " + sid);
      }
    } else if (messageType == MSG_OPEN_CHANNEL) {
      int channelType = /* 1 byte unsigned integer */ 0xFF & buffer.get();
      int priority = /* 2 bytes unsigned integer */ 0xFFFF & buffer.getShort();
      long reliability = /* 4 bytes unsigned integer */ 0xFFFFFFFFL & buffer.getInt();
      int labelLength = /* 2 bytes unsigned integer */ 0xFFFF & buffer.getShort();
      int protocolLength = /* 2 bytes unsigned integer */ 0xFFFF & buffer.getShort();
      String label;
      String protocol;

      if (labelLength == 0) {
        label = "";
      } else {
        byte[] labelBytes = new byte[labelLength];

        buffer.get(labelBytes);
        label = new String(labelBytes, "UTF-8");
      }
      if (protocolLength == 0) {
        protocol = "";
      } else {
        byte[] protocolBytes = new byte[protocolLength];

        buffer.get(protocolBytes);
        protocol = new String(protocolBytes, "UTF-8");
      }

      if (logger.isDebugEnabled()) {
        logger.debug(
            "!!! "
                + getEndpoint().getID()
                + " data channel open request on SID: "
                + sid
                + " type: "
                + channelType
                + " prio: "
                + priority
                + " reliab: "
                + reliability
                + " label: "
                + label
                + " proto: "
                + protocol);
      }

      if (channels.containsKey(sid)) {
        logger.error("Channel on sid: " + sid + " already exists");
      }

      WebRtcDataStream newChannel = new WebRtcDataStream(sctpSocket, sid, label, true);
      channels.put(sid, newChannel);

      sendOpenChannelAck(sid);

      notifyChannelOpened(newChannel);
    } else {
      logger.error("Unexpected ctrl msg type: " + messageType);
    }
  }