It sounds like you are using my ProScan or Free RadioFeed program Source Client feature.
Any error code means that the source can't communicate with the far end. The TCP protocol doesn't indicate where the problem is. It could be the computer, router, cables, ISP, & far end. The computers can be eliminated since it's happening on 3 computers.
I would first power cycle the router. If that doesn't cure the problem then reseat the Ethernet cables. I've seen some use a program called PingPlotter to narrow in on the problem.