On Server:

SQL> select * from v$version;

BANNER
----------------------------------------------------------------
Oracle8i Enterprise Edition Release 8.1.7.2.0 - Production
PL/SQL Release 8.1.7.2.0 - Production
CORE 8.1.7.0.0 Production
TNS for Solaris: Version 8.1.7.2.0 - Production
NLSRTL Version 3.4.1.0.0 - Production

OR

LSNRCTL> version
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=xyz32.oracle.com)(PORT=1521)))
TNSLSNR for Solaris: Version 8.1.7.2.0 - Production
TNS for Solaris: Version 8.1.7.2.0 - Production
Unix Domain Socket IPC NT Protocol Adaptor for Solaris: Version 8.1.7.2.0 - Production
Oracle Bequeath NT Protocol Adapter for Solaris: Version 8.1.7.2.0 - Production
TCP/IP NT Protocol Adapter for Solaris: Version 8.1.7.2.0 - Production,,
The command completed successfully



On Client:

You know what you have installed Or just open the version of the client software folders and see.