title: MPICH2 on multiple machines (HYDU_sock_connect error)
body: <p>I am trying to execute an MPI program in 2 different PCs. However, when I ran this command in pc1:</p>
  
  <pre><code>mpirun -hosts user@host -n 4 bin/Demo_01.exe 
  </code></pre>
  
  <p>I'm getting this error:</p>
  
  <pre><code>[proxy:0:0@pc2] HYDU_sock_connect (./utils/sock/sock.c:203): unable to connect from "pc2" to "pc1" (Connection refused)
  
  [proxy:0:0@pc2] main (./pm/pmiserv/pmip.c:209): unable to connect to server ubuntu at port 57395 (check for firewalls!)
  </code></pre>
  
  <p>Although I configured SSH connections as without password and disabled firewalls on each machines, the error is still there. My operating system is Ubuntu 12.04 and mpi is MPICH2.</p>
  
  <p>Is there anyone to help?</p>