Some times the port to the server has been changed, such that we must change the default port (25) to the new port. Here is the solution:
1. Find out the file ~/.subversions/config
2. Add follow line: sshtunnels=ssh -p newportnummer. Save the file and exit.
3. Checkout the server svn repository by: svn co svn+sshtunnels://hostname@hostip/pathToSvnRepository