Hi! I have a problem on one host when MPID_nem_tcp_bind() failed with "MPID_nem_tcp_bind(580): unable to bind socket to port (port=1,errno=98:Address already in use)". However, MPID_nem_tcp_bind() tried to bind to port 0 (ports ranges was not specified), then failed, and port variable was incremented before final error message recorded. MPICH_PORT_RANGE helped to solve problem on aforementioned host. I tried version 1.5 and 3.0.4. Eugene.