/**
* Sends acknowledgment for open channel request on given SCTP stream ID.
*
* @param sid SCTP stream identifier to be used for sending ack.
*/
private void sendOpenChannelAck(int sid) throws IOException {
// Send ACK
byte[] ack = MSG_CHANNEL_ACK_BYTES;
int sendAck = sctpSocket.send(ack, true, sid, WEB_RTC_PPID_CTRL);
if (sendAck != ack.length) {
logger.error("Failed to send open channel confirmation");
}
}
/**
* Opens new WebRTC data channel using specified parameters.
*
* @param type channel type as defined in control protocol description. Use 0 for "reliable".
* @param prio channel priority. The higher the number, the lower the priority.
* @param reliab Reliability Parameter<br>
* This field is ignored if a reliable channel is used. If a partial reliable channel with
* limited number of retransmissions is used, this field specifies the number of
* retransmissions. If a partial reliable channel with limited lifetime is used, this field
* specifies the maximum lifetime in milliseconds. The following table summarizes this:<br>
* </br>
* <p>+------------------------------------------------+------------------+ | Channel Type |
* Reliability | | | Parameter |
* +------------------------------------------------+------------------+ |
* DATA_CHANNEL_RELIABLE | Ignored | | DATA_CHANNEL_RELIABLE_UNORDERED | Ignored | |
* DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT | Number of RTX | |
* DATA_CHANNEL_PARTIAL_RELIABLE_REXMIT_UNORDERED | Number of RTX | |
* DATA_CHANNEL_PARTIAL_RELIABLE_TIMED | Lifetime in ms | |
* DATA_CHANNEL_PARTIAL_RELIABLE_TIMED_UNORDERED | Lifetime in ms |
* +------------------------------------------------+------------------+
* @param sid SCTP stream id that will be used by new channel (it must not be already used).
* @param label text label for the channel.
* @return new instance of <tt>WebRtcDataStream</tt> that represents opened WebRTC data channel.
* @throws IOException if IO error occurs.
*/
public synchronized WebRtcDataStream openChannel(
int type, int prio, long reliab, int sid, String label) throws IOException {
if (channels.containsKey(sid)) {
throw new IOException("Channel on sid: " + sid + " already exists");
}
// Label Length & Label
byte[] labelBytes;
int labelByteLength;
if (label == null) {
labelBytes = null;
labelByteLength = 0;
} else {
labelBytes = label.getBytes("UTF-8");
labelByteLength = labelBytes.length;
if (labelByteLength > 0xFFFF) labelByteLength = 0xFFFF;
}
// Protocol Length & Protocol
String protocol = WEBRTC_DATA_CHANNEL_PROTOCOL;
byte[] protocolBytes;
int protocolByteLength;
if (protocol == null) {
protocolBytes = null;
protocolByteLength = 0;
} else {
protocolBytes = protocol.getBytes("UTF-8");
protocolByteLength = protocolBytes.length;
if (protocolByteLength > 0xFFFF) protocolByteLength = 0xFFFF;
}
ByteBuffer packet = ByteBuffer.allocate(12 + labelByteLength + protocolByteLength);
// Message open new channel on current sid
// Message Type
packet.put((byte) MSG_OPEN_CHANNEL);
// Channel Type
packet.put((byte) type);
// Priority
packet.putShort((short) prio);
// Reliability Parameter
packet.putInt((int) reliab);
// Label Length
packet.putShort((short) labelByteLength);
// Protocol Length
packet.putShort((short) protocolByteLength);
// Label
if (labelByteLength != 0) {
packet.put(labelBytes, 0, labelByteLength);
}
// Protocol
if (protocolByteLength != 0) {
packet.put(protocolBytes, 0, protocolByteLength);
}
int sentCount = sctpSocket.send(packet.array(), true, sid, WEB_RTC_PPID_CTRL);
if (sentCount != packet.capacity()) {
throw new IOException("Failed to open new chanel on sid: " + sid);
}
WebRtcDataStream channel = new WebRtcDataStream(sctpSocket, sid, label, false);
channels.put(sid, channel);
return channel;
}