JetBrains/intellij-community · error · CantRunException

The port to attach to unspecified

Error message

The port to attach to unspecified

What it means

Error "The port to attach to unspecified" thrown in JetBrains/intellij-community.

Source

Thrown at java/debugger/impl/src/com/intellij/debugger/engine/DebugProcessImpl.java:752

        setConnectorArgument("pid", pid);
      }
      else if (myConnection.isServerMode()) {
        if (port == null) {
          throw new CantRunException(JavaDebuggerBundle.message("error.no.debug.listen.port"));
        }
        String debuggerHostName = myConnection.getDebuggerHostName();
        if (debuggerHostName != null) {
          setConnectorArgument("localAddress", debuggerHostName);
        }
      }
      else { // is client mode, should attach to already running process
        if (myConnection.isUseSockets()) {
          String debuggerHostName = myConnection.getDebuggerHostName();
          if (debuggerHostName != null) {
            setConnectorArgument("hostname", debuggerHostName);
          }
          if (port == null) {
            throw new CantRunException(JavaDebuggerBundle.message("error.no.debug.attach.port"));
          }
          setConnectorArgument("port", port);
        }
        else {
          if (port == null) {
            throw new CantRunException(JavaDebuggerBundle.message("error.no.shmem.address"));
          }
          setConnectorArgument("name", port);
        }
        setConnectorArgument("timeout", "0"); // wait forever
      }
      return connector instanceof AttachingConnector
             ? attachConnector((AttachingConnector)connector)
             : connectorListen(port, (ListeningConnector)connector);
    }
    catch (IOException e) {
      throw new ExecutionException(processIOException(e, JavaDebuggerBundle.getAddressDisplayName(myConnection)), e);
    }

View on GitHub (pinned to be881553f2)

Solutions

1. Enter the port of the target JVM to attach to in the debug configuration.
2. Make sure the target JVM was started with -agentlib:jdwp=transport=dt_socket,server=y,address=<port> and use that port.

Example fix

Target started with address=*:5005 -> set Host: localhost, Port: 5005 in the Remote JVM Debug configuration.

When it happens

Trigger: An attach-mode (socket attach) debug session is started with an empty port.

Common situations: The Port field of an Attach to remote JVM configuration is blank.

AI-assisted analysis of JetBrains/intellij-community@be881553f2 (2026-08-14). Data as JSON: /api/errors/0406d34a278d67ad. Report an issue: GitHub.