Client Recv: failed to connect to ip=localhost  - Fix

1. Server Not Running

• The most common reason for this error is that the server is not running or not properly set up.

Fix:

• Ensure that the server is started and listening on port 7777.

In Unity, if you're using Mirror, make sure the server is running via:
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NetworkManager.singleton.StartServer();

2. Mismatched Host and Port

• The client might be trying to connect to the wrong address or port.

Fix:

• Verify that the client and server are using the same address and port.

• In the Network Manager component:

  • Set the Network Address to localhost on both client and server.

  • Ensure the port (7777 by default) matches.

Example code:

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NetworkManager.singleton.networkAddress = "localhost";

NetworkManager.singleton.networkPort = 7777;

3. Firewall Blocking the Connection

• A firewall might be blocking the connection on port 7777.

Fix:

• Allow the port in your system's firewall settings:

  • Windows:

    1. Open the Windows Defender Firewall.

    2. Go to Advanced Settings → Inbound Rules.

    3. Add a new rule to allow traffic on port 7777.

  • Linux/Mac: Use iptables or equivalent tools to allow the port.

• Temporarily disable the firewall for testing (not recommended for production).

4. Server IP Address Binding

• If the server is bound to a specific IP address rather than all available ones (0.0.0.0), it may reject connections.

Fix:

• Ensure the server is listening on localhost or 0.0.0.0 for local testing.

You can use netstat to check if the server is listening on the correct address and port:
sh
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netstat -an | findstr 7777

5. Networking Code Errors

• Check your server and client setup in Mirror:

  • Ensure the server has been started (StartServer or StartHost).

  • Ensure the client calls StartClient() after setting the network address.

Example client-side code:

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NetworkManager.singleton.networkAddress = "localhost";

NetworkManager.singleton.StartClient();

6. Debugging Tips

• Log Outputs:

Add logs to confirm the server started successfully:
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Debug.Log($"Server started on {NetworkManager.singleton.networkAddress}:{NetworkManager.singleton.networkPort}");

Add logs for client connection attempts:
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Debug.Log("Client attempting to connect...");

• • 
    

• Check Server Logs:

  • Ensure no errors occurred when starting the server.

  • Verify that Mirror's transport is properly configured.

• Test with External Tools:

Use tools like telnet or nc to test if the port is open:
sh
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telnet localhost 7777

Common Unity Mirror Setup Example

Here’s a simple example to ensure everything is configured correctly:

Server:
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void Start()

{

    NetworkManager.singleton.StartServer();

    Debug.Log("Server started.");

}

Client:
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void Start()

{

    NetworkManager.singleton.networkAddress = "localhost";

    NetworkManager.singleton.StartClient();

    Debug.Log("Client connecting to server...");

2. }