Hi guys,
I’m new to the Editor and have the same problem. I don’t have much experience about portforwarding and things like these but I’m using a tool named “iNetfusion” wich combines two internet-connections to double my speed. Once I’ve started the vanilla version of WoW it crashed because of some connection problems. I had no idea why because it ran well all the time so I just stopped the service of iNetfusion and it worked. Now I got that error in ue4 and just googled about it and found your thread. After reading a bit and saw that problem with the localhost and the port I just stopped once again the iNetfusion service und swarm could connect to the coordinator without any problem.
Maybe u’r using the same tool or it may can give you a hint to solve your problem. Maybe u just download that iNetfusion thing an restart that service inside that program. (it is not directly a separate service installes by iNetfusion. That program just do something with your ports and so on.) U may just give it a try…
hope I could help anyway