Taxes applicable on Online Services

Dear Team, I wish to start an online portal (in India) wherein service providers and service seekers (collectively "portal users") shall post their needs and the portal shall match the requirements, showing contact details of the interested parties. So basically, I am only providing a platform to connect the actual service provider with service seeker and vice versa; by charging them a nominal portal subscription fees. The portal users may use portal's messaging platform for discussions or may discuss the same offline (through phone or their emails) and finalize the deal (portal has no business in finalization, neither we are charging any commission). The actual service shall be provided offline (i.e. not through our portal), directly from service provider to the service seeker. The portal users may be based anywhere in the world (of course including India) and may be making online payment towards portal subscription in foreign currency(ies). I would request if you can throw some light on the taxes (ST or VAT or any other such taxes) applicable on me towards receiving the subscription fees. Will it be different for an Indian user and Foreign user? Thanks in advance, Regards, Anuj Gupta.