Sharing licenses across UNIX and Windows architectures is possible using the <port>@<host> functionality available in FLEXlm v6.0 (and higher). This functionality relies on TCP/IP protocol for direct communication with the license server daemon (ESRI) on a heterogeneous network.
Setting the ESRI_LICENSE_FILE environment variable enables the <port>@<host> functionality. This variable is set in a client's environment, not on the server side. Both <port> and <host> are found in the SERVER line of your license file. The TCP/IP <port> is indicated at the end of the SERVER line. The host name, <host>, is the second item listed in the SERVER line.