Find what you see.

Please start with the FAQ questions below: most trouble is one of these. Each has the same label on every page, Q1 to Q10. Then the problems we know for this step, each with its cause and fix.

1. Q7

   Was the Windows firewall prompt answered Deny, or closed without an answer?

   How to tell: Either one adds Block rules for the program, and a Block rule wins over every Allow rule, Steam's included. The host then hears no joins: the joining PC shows "No answer from …" after 8 seconds, and the host stays on "No guest yet".

   What to do: Please open Windows Security › Firewall & network protection › Advanced settings › Inbound Rules. Delete the Block rules naming roomMicApp.exe. Start CO-OP Comms, press Host, and answer the prompt Allow with Private networks ticked. If the network is set to Public, set it to Private in Settings › Network & internet › Ethernet (or Wi-Fi) › Network profile type, or allow the app on Public too.

   On CO-OP Comms Client Only: On the Client Only PC, please delete the Block rules that name roomMicClient.exe. Client Only receives the sound on UDP 47800 and the host list on UDP 47801, so a Block rule there stops both.

2. Q6

   Are both PCs on the same subnet, and able to reach each other?

   How to tell: CO-OP Comms is made for two PCs on the same subnet of one local network. The list of hosts stays on the local network: it reaches every PC on the same subnet (PCs plugged into the same router or switch), it never goes out to the WAN (the internet), and it does not pass between two separate subnets in one building. Compare the two addresses: each PC shows its own under This PC on its start screen. On most home and office networks, PCs on one subnet have addresses whose first three numbers match, such as 192.168.1.160 and 192.168.1.21; 192.168.1.160 and 192.168.5.40 are on different subnets. Matching numbers are not proof. Guest Wi-Fi, Wi-Fi that keeps devices apart ("AP isolation" or "client isolation"), separate VLANs, a DMZ, or a test lab that isolates each machine look the same in the numbers and still keep the PCs apart. The signs are in the windows: the host is hosting, but the joining PC's list stays empty after 10 seconds, and a typed address gets "No answer from …" after 8 seconds. On Wi-Fi, once linked, a grey line reads "This PC is on Wi-Fi. CO-OP Comms is made for wired Ethernet; over Wi-Fi, expect more delay and gaps in the sound."

   What to do: Please plug both PCs into the same router or switch with a cable, on the main network, not a guest network. On a managed or test network, please ask your IT staff: "These two PCs need to reach each other directly on one local network: the same subnet, with no client isolation or firewall between them, and UDP ports 47800 and 47801 allowed both ways. Can you please put them there?" The rule: the list finds hosts on the same subnet only; typing the host PC's address is tried for any address, private or public, on another subnet too. It links when the network between the PCs lets UDP port 47800 through both ways; machines kept apart still will not connect. We test one subnet, and have not yet tried a typed join across a router.

   On CO-OP Comms Client Only: Client Only has no "This PC" line. Its own address shows in the Network picker, such as "Ethernet · 192.168.1.21". Read the host's address from the host's "This PC" line.

3. Q10

   Are both PCs on version 0.2.2?

   How to tell: Only 0.2.2 shows JOINING while it waits for the host, and the timed warnings these steps quote. 0.2.1 shows JOINED at once.

   What to do: Let Steam update both PCs. Mixed versions still link, since the packet format did not change.

   On CO-OP Comms Client Only: Client Only 0.2.1 also shows JOINED at once, with none of the timed warnings.

Problems we know for step 2C

1. 2C-1

   I see No answer from host's Steam user name. The host was in the list, so check that CO-OP Comms is still hosting there. A firewall or a Mac's Local Network setting on the host PC can block it.

   Words shaded like this stand for what your own screen shows there, such as your own user name or address.

   An amber line, after 8 seconds of JOINING.

   Why

   The host's firewall blocked the join (Q7), the most likely after a Deny; or the host pressed Leave; or the network passes the list but keeps the two PCs from reaching each other (Q6).

   Fix

   Check that the host PC still shows HOSTING. If it does, go through Q7 on the host PC, then Q6.

   Show it in CO-OP Comms Client Only

2. 2C-2

   I see The host is talking to someone else.

   Under "Turned away by the host".

   Why

   Another PC is already joined to the host.

   Fix

   Press Leave on the other joining PC, then press Join again.

   Show it in CO-OP Comms Client Only

3. 2C-3

   I see That host is no longer in the list. It may have stopped hosting. Or: That host already has a guest. Join it when it no longer says busy.

   A red banner, when Join is pressed.

   Why

   The host left, or turned busy, just as Join was pressed.

   Fix

   On the host PC, check that it shows HOSTING with "No guest yet"; press Host if it does not. Then press Join again once the host's row is back in the list without "· busy".