Warning: Unrecognized client name "XXX", check server config

I had the same problem, the problem appears to be caused when the host doesn't recognize the client screen-name. However, there also appears to be a bug somewhere between settings in a config file and setting made 'interactively'. I've outlined how to reproduce and how to fix:

Quick Check

Make sure the screen name of the client (Edit->Settings on Windows synergy.exe as client) matches the screen name assigned to the client in the Server (Configure interactively->Configure Server on Windows synergy.exe as server)

To reproduce buggy behaviour

1. Configure server interactively (using synergy.exe on Windows) and provide the wrong screen name for the client.
2. Try to connect with the client and confirm you get the expected unrecognised client name warning
3. Save the Server config (File->Save configuration as...)
4. Set the Server to use the config (ie select Use existing configuration and provide path to config file)
5. Edit the config file, and change the wrong screen-name to the correct screen-name.
6. Start the server.
7. I still see the same error, even though the config is now correct.

Fix

1. Configure server interactively, and provide the correct screen-name for the client
2. Optionally, save the Server config (although the output config file will be identically to the one you manually repaired previously)
3. Optionally, run the Server with interactive setup and confirm a connection can be made.
4. Run the Server with the config, and confirm a connection can be made.

The only conclusion I can come to is the client screen name that is set under the 'interactive' settings interferes with the client screen names seen in the config. Since the interactive settings persist between instances of synergy.exe we know that information is being stored, but I haven't found where.

I had this exact issue, but then thought about RamonLion's suggestion and solved my issue:

1. Create the server
2. Leave "configure interactively" set
3. Click configure server
4. drag the computer icon from the top right into the grid
5. double click the new icon, change the screen name to match your new client's computer name ie "laptop"
6. click OK
7. click OK
8. On the Client, select "Client"
9. set the server IP to match the server ip. Click Apply.
10. click "Apply" (this is the key I was missing), it needs to restart the server with the new clients.

WARNING: unrecognised client name "HOSTNAME", check server config

... means the host name can not be recognised. This is a NetBIOS name an when this name not be recognised then use a full qualified domain name e.g. hostname.mydomain.org

Set this client name in both server and client config et viola!

NOTE: started server, waiting for clients

NOTE: accepted client connection

NOTE: client "hostname.mydomain.org" has connected

I'm running Windows 8 Pro x64 and have the same errors.

Client I get: WARNING: failed to connect to server: server refused client with our name NOTE: connecting to 'HTPC-JON': 10.19.1.135:24800 ERROR: server refused client with name "JazPadW520"

Server I get: NOTE: accepted client connection WARNING: unrecognised client name "JazPadW520", check server config NOTE: disconnecting client "JazPadW520" NOTE: client "JazPadW520" has disconnected NOTE: accepted client connection

I drag'd & drop'd the computer icon, and named it "JazPadW520" I still get the same errors above though!

EDIT!!!!!! Whoops, I forgot to hit APPLY on the server after I made the icon as said above by gollumullog It's connecting now great

Uncheck the elevate checkboxes before following the instructions in the answer above. This wont work with those active.