And (drumroll.... ) it works.. i copied the unix C sources for ssl plugin, changed 2 lines of code (to include SSL.h before sq.h because of conflicting definitions) and i were able to compile & link it: $ make SqueakSSL [100%] Building C object SqueakSSL/CMakeFiles/SqueakSSL.dir/C_/COG/blessed/src/plugins/SqueakSSL/SqueakSSL.c.obj [100%] Building C object SqueakSSL/CMakeFiles/SqueakSSL.dir/C_/COG/blessed/platforms/win32/plugins/SqueakSSL/sqUnixOpenSSL.c.obj c:/COG/blessed/platforms/win32/plugins/SqueakSSL/sqUnixOpenSSL.c: In function 'sqSetupSSL': c:/COG/blessed/platforms/win32/plugins/SqueakSSL/sqUnixOpenSSL.c:51:14: warning: assignment discards 'const' qualifier from pointer target type [enabled by default] Linking C shared library /C/COG/blessed/results/SqueakSSL.dll Creating library file: c:/COG/blessed/results/libSqueakSSL.dll.a [100%] Built target SqueakSSL and then run the tests (see screenshot). so, next step would be is to properly integrate it with library bundling mechanism to make sure cmake will automatically download , make & link openssl library used by plugin. (if you want i can send you the binaries of built plugin for more serious testing) -- Best regards, Igor Stasenko.