VB.Net Simple server/client Web Service

Hi Experts
I have a small VB.Net forms app out with our sales people and remote offices.
They all have internet access.
I would like the app to send a small amount of data toa server at head office and receive a short acknowledgment back
The amount of data in each case would be very small.
I can achieve this simply with sockets but am concerned about firewalls etc
I would think that a simple client/server  web service would be more suitable but have never tried it.
Can someone give me some advise on this and if a web service is considered best, where I could start?
Code examples would be great
Thanks in advance