add top-level sendPing method to connections

core/src/main/groovy/com/muwire/core/connection/Connection.groovy

@@ -95,4 +95,11 @@ abstract class Connection implements Closeable {
 	}
 	
 	protected abstract void write(def message);
+	
+	void sendPing() {
+		def ping = [:]
+		ping.type = "Ping"
+		ping.version = 1
+		messages.put(ping)
+	}
 }

core/src/main/groovy/com/muwire/core/connection/UltrapeerConnection.groovy

@@ -27,8 +27,18 @@ class UltrapeerConnection extends Connection {
 
 	@Override
 	protected void write(Object message) {
-		// TODO Auto-generated method stub
-		
+		if (message instanceof Map) {
+			writeJsonMessage(message)
+		} else {
+			writeBinaryMessage(message)
+		}
 	}
 
+	private void writeJsonMessage(def message) {
+		
+	}
+	
+	private void writeBinaryMessage(def message) {
+		
+	}
 }