RE: Web Services for Microsoft Dynamics NAV 2016
I'm not familiar with WAP either, but as Stefano noted, it should be easy to expose just one port for ODATA (or SOAP, depending on which type you're looking to open up). Your router / firewall can help you limit the addresses from which someone can connect to the port, or have a different external port number map to the port defined for ODATA or SOAP in NAV (by default, they are 7048 and 7047, respectively).
Also, what authentication type are using for NAV? Are you using an SSL cert with the NAV service tier (highly recommended, otherwise your data is traveling unencrypted). If using NavUserPassword as the authentication method, make sure you don't enter your default password to authenticate from the web service call. You'll need to use Web Service Access Key as your password (along with your user name as the username).
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