Add rudimentary PLH support

modules/core/src/main/java/com/illposed/osc/OSCParser.java

@@ -9,6 +9,8 @@
 import com.illposed.osc.argument.ArgumentHandler;
 import com.illposed.osc.argument.handler.IntegerArgumentHandler;
 import com.illposed.osc.argument.handler.TimeTag64ArgumentHandler;
+import com.illposed.osc.transport.NetworkProtocol;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import java.nio.Buffer;
@@ -223,7 +225,20 @@ private OSCBundle convertBundle(final ByteBuffer rawInput) throws OSCParseExcept
 	 * Assumes that the byte array is a message.
 	 * @return a message containing the data specified in the byte stream
 	 */
-	private OSCMessage convertMessage(final ByteBuffer rawInput) throws OSCParseException {
+	private OSCMessage convertMessage(final ByteBuffer rawInputWithLength) throws OSCParseException {
+
+		// remove the first four bytes, which is the frame length
+		// ideally we would use this to collect data from multiple incoming TCP packets, but for this will at least allow parsing to work for single packets
+		// we should only do this with TCP connections
+		ByteBuffer rawInput = null;
+		if ((properties.get("networkProtocol") == NetworkProtocol.TCP)&&(rawInputWithLength.limit() > 4)) {
+			rawInput = ByteBuffer.allocate(rawInputWithLength.limit() - 4);
+			for(int i = 4; i < rawInputWithLength.limit(); i++) {
+				rawInput.put(i - 4, rawInputWithLength.get(i));
+			}
+		} else {
+			rawInput = rawInputWithLength;
+		}
 
 		final String address = readString(rawInput);
 		final CharSequence typeIdentifiers = readTypes(rawInput);

modules/core/src/main/java/com/illposed/osc/OSCSerializer.java

@@ -246,6 +246,28 @@ private void writeArguments(final OSCMessage message) throws OSCSerializeExcepti
 	private void write(final OSCMessage message) throws OSCSerializeException {
 		writeAddress(message);
 		writeArguments(message);
+		if (properties.get("networkProtocol") == NetworkProtocol.TCP) {
+			writePLH();
+		}
+	}
+
+	/**
+	 * Serializes a packet length header. Call this after writing the message and arguments.
+	 * @throws OSCSerializeException if the message failed to serialize
+	 */
+	private void writePLH() throws OSCSerializeException {
+		byte[] rawOutput = output.toByteArray();
+		int length = rawOutput.length;
+		byte[] newOutput = new byte[4 + length];
+		ByteBuffer.wrap(newOutput).putInt(length); // add the length
+		ByteBuffer.wrap(newOutput, 4, length).put(rawOutput); // add the message content
+
+		output.clear();
+		output.put(newOutput);
+
+		if (false) { // what to check here?
+			throw new OSCSerializeException("Error adding packet length header");
+		}
 	}
 
 	/**

modules/core/src/main/java/com/illposed/osc/OSCSerializerAndParserBuilder.java

@@ -29,6 +29,10 @@ public OSCSerializerAndParserBuilder() {
 		this.usingDefaultHandlers = true;
 	}
 
+	public void setNetworkProtocol(NetworkProtocol networkProtocol) {
+		this.properties.put("networkProtocol", networkProtocol);
+	}
+
 	// Public API
 	@SuppressWarnings("WeakerAccess")
 	public Map<Character, ArgumentHandler> getIdentifierToTypeMapping() {

modules/core/src/main/java/com/illposed/osc/transport/OSCPortInBuilder.java

@@ -48,6 +48,7 @@ public OSCPortIn build() throws IOException {
 
 		if (parserBuilder == null) {
 			parserBuilder = new OSCSerializerAndParserBuilder();
+			parserBuilder.setNetworkProtocol(networkProtocol);
 		}
 
 		if (packetListeners == null) {

modules/core/src/main/java/com/illposed/osc/transport/OSCPortOutBuilder.java

@@ -30,6 +30,7 @@ public OSCPortOut build() throws IOException {
 
 		if (serializerBuilder == null) {
 			serializerBuilder = new OSCSerializerAndParserBuilder();
+			serializerBuilder.setNetworkProtocol(networkProtocol);
 		}
 
 		return new OSCPortOut(