If you decide to add "export MOTECOM= ..." to your environment variables be aware that it affects SerialForwarder as well. example of something you might have in your environment variables initialization file: #eMote programming export MOTECOM=network@192.168.0.2:10002 In this situation, it forces all clients to try to connect to the serialforwarder at that port, regardless of how you start SerialForwarder. i.e. java net.tinyos.sf.SerialForwarder -comm network@192.168.0.5:10002 If you forget this, you may be confused why none of your java clients can connect to SerialForwarder when you switch programming boards. This can be a particularly common mistake if you are using multiple ethernet programming boards on the network and switching between them as the basestation. If you are having strange problems with SerialForwarder, make sure to check your environment variables to see if you have MOTECOM defined!!