Diagramming server connections in Visio - what direction should arrows point?

Suppose I would like to depict data flow between two servers in Visio.

I have boxes to represent servers and arrows to represent communication / data flow.

In this situation:

Server A always initiates connections to Server B.
Server A reads from server B, but does not write.

How would this be depicted? Which way would the arrows point?

Is there are convention used for arrows connecting these two servers? Is it based on...

Which server initiates connections to the other
Whether the operation is read, write, or both

Solution

Well, that really depends on the purpose of the diagram :-)

We deal mostly with network infrastructure so we would use the arrows pointing in the direction of session establishment - this would assist us in defining firewall rules for all our zones.

But, if you're diagramming an application and you need to know data flow for the application, you'd use arrows depicting the flow of data, not session estasblishment.

I would think that, as long as the chart made it clear what you were representing, you could go either way. You could even do a hybrid solution with, for example, the arrows at the end showing data flow while you have a smaller arrow in the middle showing direction of session establishment - as long as you still document, on the chart, what it means.

No idea if Visio has that sort of arrow line - I'd just use two of them, one overlapping the other.