Add support for tunneling TCP/IP connections.

examples/src/main/java/net/schmizz/sshj/examples/Jump.java

@@ -0,0 +1,50 @@
+package net.schmizz.sshj.examples;
+
+import net.schmizz.sshj.SSHClient;
+import net.schmizz.sshj.common.IOUtils;
+import net.schmizz.sshj.connection.channel.direct.DirectConnection;
+import net.schmizz.sshj.connection.channel.direct.Session;
+
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * This example demonstrates connecting via an intermediate "jump" server using a direct TCP/IP channel.
+ */
+public class Jump {
+    public static void main(String... args)
+            throws IOException {
+        SSHClient firstHop = new SSHClient();
+
+        firstHop.loadKnownHosts();
+
+        firstHop.connect("localhost");
+        try {
+
+            firstHop.authPublickey(System.getProperty("user.name"));
+
+            DirectConnection tunnel = firstHop.newDirectConnection("localhost", 22);
+
+            SSHClient ssh = new SSHClient();
+            try {
+                ssh.loadKnownHosts();
+                ssh.connectVia(tunnel);
+                ssh.authPublickey(System.getProperty("user.name"));
+
+                final Session session = ssh.startSession();
+                try {
+                    final Session.Command cmd = session.exec("ping -c 1 google.com");
+                    System.out.println(IOUtils.readFully(cmd.getInputStream()).toString());
+                    cmd.join(5, TimeUnit.SECONDS);
+                    System.out.println("\n** exit status: " + cmd.getExitStatus());
+                } finally {
+                    session.close();
+                }
+            } finally {
+                ssh.disconnect();
+            }
+        } finally {
+            firstHop.disconnect();
+        }
+    }
+}