mainly to avoid using 80 or 8080 which are often already used (by current webserver, or even skype, or jenkins, or ...)
Make sure to have the Clib generated in the related cURL library - if you use EiffelStudio >= 7.0 check %ISE_LIBRARY%\library\cURL\spec\%ISE_C_COMPILER%\$ISE_PLATFORM or $ISE_LIBRARY/library/cURL/spec/$ISE_PLATFORM - otherwise if you use earlier version check under ext/ise_library/curl/spec/... And on Windows, be sure to get the libcurl.dll from %ISE_LIBRARY%\studio\spec\%ISE_PLATFORM%\bin\libcurl.dll