Added keep-alive mechanism that detects disconnects (Fixes #166)

src/main/java/net/schmizz/keepalive/Heartbeater.java

@@ -0,0 +1,34 @@
+/**
+ * Copyright 2009 sshj contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package net.schmizz.keepalive;
+
+import net.schmizz.sshj.common.Message;
+import net.schmizz.sshj.common.SSHPacket;
+import net.schmizz.sshj.connection.ConnectionImpl;
+import net.schmizz.sshj.transport.TransportException;
+
+final class Heartbeater
+        extends KeepAlive {
+
+    Heartbeater(ConnectionImpl conn) {
+        super(conn, "heartbeater");
+    }
+
+    @Override
+    protected void doKeepAlive() throws TransportException {
+        conn.getTransport().write(new SSHPacket(Message.IGNORE));
+    }
+}