Reverse connection and port forwarding

This page describes how to configure a paraview client/server reverse connection between a compute node cluster and your desktop when it is not possible to open a direct connection between compute node and desktop. A common situation is that compute nodes are only accessible from login nodes.

The setup using reverse connection and portfwd

Using a reverse connection the paraview client will bind to port 11111 and wait for an incoming connection from the server. When the mpi enabled paraview server (referred to as pvserver) is launched on a set of compute nodes, the 0th pvserver process opens a connection to the host machine where the paraview client is waiting.

The problem arises when it is not possible for the compute node to connect to the host machine- the compute node can only connect to a login node. The problem is solved by forwarding traffic from a port on the login node to a port on the host machine. This can be accomplished using a simple utility called portfwd found at http://portfwd.sourceforge.net/.

For this example, lets say the paraview client is waiting for a reverse connection on port 11111 of host client_host (client_host:11111), and the compute node can only connect to port 11111 of host login_node (login_node:11111). In this example pvserver is launched on the compute nodes using the command:

mpirun -np 512 pvserver --reverse-connection --client-host login_node --server-port 11111

Next, we use portfwd to forward login_node:11111 to client_host:11111. In some situtations it is possible to accomplish the kind of port fowarding using ssh tunnels, but portfwd is much simpler. First write a configuration file, fwd.cfg:

  /*
  fwd.cfg
  forwards localhost:11111 to client_host:11111
  */
  
  tcp { 11111 { => client_host:11111 } }

Then launch portfwd on the login node (this example uses the flag --foreground to keep portfwd running in the foreground so it can be killed with control-c):

portfwd --config fwd.cfg --foreground

Now when the pvserver connects to login_node:11111 the traffic will be forwarded to client_host:11111.