How to increase XMPP file transfer speed?

Question

XMPP

Good evening.
I have an enterprise XMPP (ejabberd), there are a number of computers with WinXP and Spark 2.7.4 as a client. Between them files are transferred with excellent speed.
Several Win7 computers have appeared on the network, which are also trying to send files to other users.
Now the picture looks like this:
WinXP-WinXP = OK
WinXP-Win7 = OK
Win7-WinXP = OOOOO Very slow file transfer
I've already rummaged through all the settings, updated the drivers for the network cards, no results. Ideas are over.
Maybe someone has come across such a beard and throw fresh ideas?

Answer 1

Files can be transferred in XMPP in several ways:
If desired, you can find XEPs describing this case. P2P works in Miranda and QIP.
In your case, it may turn out that the Windows 7 firewall prohibits direct connections, and the file transfer goes in pieces through the server.