Two major changes from the SunOS 4 environment hold true for SunOS 5.10 releases. The binary compatibility package enables dynamically linked socket applications that are based on SunOS 4 to run on SunOS 5.10.
You must explicitly specify the socket library (-lsocket or libsocket) on the compilation line.
You might also need to link with libnsl by using -lsocket -lnsl, not -lnsl -lsocket.
You must recompile all SunOS 4 socket-based applications with the socket library to run in a SunOS 5.10 environment.