Two people same IP cannot join same server in BF4

[narcionick]

So in my case, after doing some further investigation I've managed to work around the issue. I'll try to explain a bit so that others can try a similar solution for themselves if they have the same problem.

BF4's executable connects from local port 3659 to the remote server on the internet that you're trying to connect to. In my case I have a NAT router which connects my local network with 2 computers behind it to the internet connection. When computer A sends data to an internet server on port 3659, the NAT sees this, and any return data coming from the internet server back to port 3659 gets routed to computer A. When computer B sends data to that same internet server on port 3659, the NAT has already established that return data from that internet server is going to computer A, and thus computer B gets nothing back and can't connect / play.

The solution for me was putting a setting back on in my router that randomizes the local ports that the data was being sent from. Ie, computer A sends data out from port 3659, the NAT intercepts it, changes it to a random port, say 30000, then sends that data out to the remote BF4 server. When that BF4 server sends data back, it sends it to port 30000, and thats routed to computer A on port 3659. Then when computer B tries to send data out to that same BF4 server on port 3659, again, the NAT changes that port to something random, say 40000, and when the BF4 server returns the data, it comes back to port 40000, and the NAT knows to send that data to computer B port 3659. By this method we're both able to connect with no problems.

Again in my case, I had that local port randomization disabled in my NAT because I was troubleshooting another unrelated problem, and forgot to turn it back on.

Another solution to this problem would be to simply change the local port that the BF4 executable tries to send data out on. I don't know how to do this, but it should be a simple command line argument. If you could do this, and each put your own BF4s to different local ports, you should be able to connect without having to mess with your router (if this is the problem.)

Another way to get around this is to use a program called "Smart Port Forwarding" or something similar, which basically intercepts your data that your computer is sending out on port 3659, and changes that port to something else. If your two or more computers on the same local network are all using different ports, the NAT will be able to send the data out to each computer as it returns from the internet BF4 server. You should be able to search for that program, I'm not sure if I can post an external link on this forum.

I hope this helps.

-N

[DavidFishy87]

Has anybody had any further luck with this?

I've already tried:

- Disabling UPNP in my router.
- Put one of the computers in the DMZ, but that still keeps the same external IP so that doesn't work either.
- Get one computer on WiFi in the hopes that the router would be smarter, but it isn't.
- Disable UPNP and SSDP services on all relevant computers.
- Disabled network sharing and discovery on both computers.
- Edited the AppExePath registry setting for both x86 and 64bit versions of the exe to have +network.clientport
27xxx behind them (different ports on all computers).
Alternatively I've tried adding different ports, or changed "+network.clientport" into just "clientport" as I've read somewhere (though in less places) that I should use that.
The key in question can be found in
HKLM\Software\Microsoft\Widnows\CurrentVersion\GameUX\Games\"SSID for the game"

I've changed both the 64 and 32 bit ports, but no difference. So I'm really hoping anyone has any idea here.

Btw: Sometimes it does work, but I've been unable to find a constant factor in the behaviour.

[calebisstupid]

Having the same issue: followed all instructions in this thread and no luck. Here is our scenario:

* we have 5 PCs all on LAN (4 wired, 1 wireless).
* PC A and B always disconnect each other (one tries to join, both get disconnected)

* All remaining PCs are fine: can have 4 players playing as long as both A and B do not try and connect

Performed manual router reset, port forwardining, etc etc etc. Cannot seem to isolate the problem.

UPDATE: literally this second we just had computer C disconnect computer D. I have no idea how we had 4 players playing together at once. We have been troubleshooting this issue for about 4 straight hours and testing all on the same server for consistancy.

[Wedgorek]

HEY  !? Having the same issue can't play with my mate from the same house!

Im not supposed to change ports etc Ea is taking heavy loads of money for BF4 and they can't do simple things? Common!

It looks like EA didn't learn anything... 

AGAIN FAIL!

[incredibletintin]

same sh&$$t

let me know if u guys find out how to fix this

[Spinkick]

Its probably a security thing. In some routers, there are different types of NAT. I will have to test and see if I can get around it. Another option (while expensive) is to get a block of static ip addresses from your provider so that each person's computer has a different public ip address. This would definately work.

Look for something that pertains to NAT. It depends on the router, some call it strict nat, you want that disabled. On mine its "restrict forwarding rules to ip" and I have it turned off. The issue is that you want to make sure the traffic does not go to one pc or the other. This is why upnp has to be turned off. UPNP is actually setting up forwarding rules automatically to one machine or the other..You should not have to forward any ports to your machines, and if you do, the forwarding rules are taking all that inbound traffic and sending it to one machine. Also, dont DMZ just one machine, because you are in effect doing the same thing. Let me know if this gives you any clues. Tough to say without your router. 

[MinerMatthew2012]

Yes, one of the previous posters was correct.

1. Log in to your home router and disable uPnP.

 then, for both computers:

2. In Windows, Go to Start > Run and type in Services.msc
3. Stop the "UPnP Device Host" service.
4. Stop the "SSDP Discovery" service.

I'm a bit annoyed, 2 players used to work for the 1st week after the release. Then it started disconnecting as described.
EA didn't help at all. The community solved it.

And apparently the problem occurred in BF3 also. You think they'd have added this solution to their known problems page.

[signalgrau]

I solved this problem by forwarding these ports on my router to my ip:

https://help.ea.com/article/online-ports-for-battlefield-3Quote

[locko6]

My flatmate and i had the same issue, tired chageing ports and disabling UPNP, doing all that with no luck, kept reading forums and chaging alot of things, after a couple of hours no luck, i thort maybe if connected to wireless and he connected to cable that it might work. gave it a shot and it worked , not sure if it had been suggested somewhere else, but it works for us.

[hvk-_-]

man i just started having that exact issue with the latest update (china rising). Nothing changed in my router config. Whats the deal?