JetBrains/intellij-community · error · IOException

Debugger is already listening

Error message

Debugger is already listening

What it means

Error "Debugger is already listening" thrown in JetBrains/intellij-community.

Source

Thrown at java/debugger/impl/src/com/intellij/debugger/engine/DebugProcessImpl.java:722

        try {
          if (thread.frameCount() > 0) {
            StackFrameProxyImpl stackFrame = thread.frame(0);
            if (stackFrame != null) {
              return stackFrame.location();
            }
          }
        }
        catch (EvaluateException ignored) {
        }
      }
    }
    return null;
  }

  private VirtualMachine createVirtualMachineInt() throws ExecutionException {
    try {
      if (myArguments != null) {
        throw new IOException(JavaDebuggerBundle.message("error.debugger.already.listening"));
      }

      final String port = myConnection.getDebuggerAddress();

      Connector connector = getConnector();
      myArguments = connector.defaultArguments();
      if (myConnection instanceof PidRemoteConnection && !((PidRemoteConnection)myConnection).isFixedAddress()) {
        String pid = ((PidRemoteConnection)myConnection).getPid();
        if (StringUtil.isEmpty(pid)) {
          throw new CantRunException(JavaDebuggerBundle.message("error.no.pid"));
        }
        setConnectorArgument("pid", pid);
      }
      else if (myConnection.isServerMode()) {
        if (port == null) {
          throw new CantRunException(JavaDebuggerBundle.message("error.no.debug.listen.port"));
        }
        String debuggerHostName = myConnection.getDebuggerHostName();

View on GitHub (pinned to be881553f2)

Solutions

1. Stop the existing debug session before starting a new one on the same configuration.
2. Use a different port if you intentionally run two debugger listeners.

Example fix

Click the red Stop button in the Debug tool window, then start debugging again.

When it happens

Trigger: A remote/debug 'listen' session is started while another debugger session is already listening.

Common situations: Re-running a Listen-style remote debug configuration without terminating the previous session.

AI-assisted analysis of JetBrains/intellij-community@be881553f2 (2026-08-14). Data as JSON: /api/errors/6be59bfd6596be78. Report an issue: GitHub.