[SOLVED] Connecting to Mongo database through SSH tunnel in Java

Issue

FIXED (edited code to reflect changes I made)

I'm trying to connect to a Mongo database through an SSH tunnel using Java.

I'm using the Mongo driver 3.0.2 and jcraft (JSch) to create an SSH tunnel. The idea is that I:

• connect to the machine hosting the MongoDB installation through SSH
• set up port forwarding from a local port to the remote MongoDB port
• connect to MongoDB remotely

My code looks like this:

// forwarding ports
private static final String LOCAL_HOST = "localhost";
private static final String REMOTE_HOST = "127.0.0.1";
private static final Integer LOCAL_PORT = 8988;
private static final Integer REMOTE_PORT = 27017; // Default mongodb port

// ssh connection info
private static final String SSH_USER = "<username>";
private static final String SSH_PASSWORD = "<password>";
private static final String SSH_HOST = "<remote host>";
private static final Integer SSH_PORT = 22;

private static Session sshSession;

public static void main(String[] args) {
try {
    java.util.Properties config = new java.util.Properties();
    config.put("StrictHostKeyChecking", "no");
    JSch jsch = new JSch();
    sshSession = null;
    sshSession = jsch.getSession(SSH_USER, SSH_HOST, SSH_PORT);
    sshSession.setPassword(SSH_PASSWORD);
    sshSession.setConfig(config);
    sshSession.connect();
    sshSession.setPortForwardingL(LOCAL_PORT, REMOTE_HOST, REMOTE_PORT);

    MongoClient mongoClient = new MongoClient(LOCAL_HOST, LOCAL_PORT);
    mongoClient.setReadPreference(ReadPreference.nearest());
    MongoCursor<String> dbNames = mongoClient.listDatabaseNames().iterator();
    while (dbNames.hasNext()) {
    System.out.println(dbNames.next());
    }
} catch (Exception e) {
    e.printStackTrace();
} finally {
    sshSession.delPortForwardingL(LOCAL_PORT);
    sshSession.disconnect();
}
}

This code, when run, doesn't EDIT: does work. Connecting to the SSH server works just fine, but connecting to the Mongo database behind it doesn't work and returns this error:

INFO: Exception in monitor thread while connecting to server localhost:8988
com.mongodb.MongoSocketReadException: Prematurely reached end of stream
    at com.mongodb.connection.SocketStream.read(SocketStream.java:88)
    at com.mongodb.connection.InternalStreamConnection.receiveResponseBuffers(InternalStreamConnection.java:491)
    at com.mongodb.connection.InternalStreamConnection.receiveMessage(InternalStreamConnection.java:221)
    at com.mongodb.connection.CommandHelper.receiveReply(CommandHelper.java:134)
    at com.mongodb.connection.CommandHelper.receiveCommandResult(CommandHelper.java:121)
    at com.mongodb.connection.CommandHelper.executeCommand(CommandHelper.java:32)
    at com.mongodb.connection.InternalStreamConnectionInitializer.initializeConnectionDescription(InternalStreamConnectionInitializer.java:83)
    at com.mongodb.connection.InternalStreamConnectionInitializer.initialize(InternalStreamConnectionInitializer.java:43)
    at com.mongodb.connection.InternalStreamConnection.open(InternalStreamConnection.java:115)
    at com.mongodb.connection.DefaultServerMonitor$ServerMonitorRunnable.run(DefaultServerMonitor.java:127)
    at java.lang.Thread.run(Unknown Source)

I've tried doing this through command line as follows:

$ ssh <user>@<host> -p 22 -X -C
$ <enter requested password>
<user>@<host>$ mongo
<user>@<host>$ MongoDB shell version: 2.6.10
<user>@<host>$ connecting to: test

So this seems to work. I'm at a loss as to why the Java code (which should be doing roughly the same thing) doesn't work.

Solution

I managed to make it work (tried to forward port to "localhost" rather than "127.0.0.1", changing it fixed it) edit: I guess the server was listening specifically on localhost rather than 127.0.0.1

Answered By - David V

Answer Checked By - Robin (WPSolving Admin)