What causes "Unsupported operation getPort()" in grpc/grpc-java?

Stop calling getPort() on UdsSocket; a Unix domain socket has no port — derive endpoint info from the socket file path instead

grpc/grpc-java · info · UnsupportedOperationException

Unsupported operation getPort()

Error message

Unsupported operation getPort()

What it means

UdsSocket wraps a LocalSocket for Unix-domain-socket gRPC transport on Android. java.net.Socket's getPort() has no meaning for a UDS (there is no TCP port), so the override unconditionally throws UnsupportedOperationException. It exists only to satisfy the Socket abstract API; callers must not invoke it.

Source

Thrown at android/src/main/java/io/grpc/android/UdsSocket.java:148

  @Override
  public boolean getOOBInline() {
    throw new UnsupportedOperationException("Unsupported operation getOOBInline()");
  }

  @Override
  public OutputStream getOutputStream() throws IOException {
    return new FilterOutputStream(localSocket.getOutputStream()) {
      @Override
      public void close() throws IOException {
        UdsSocket.this.close();
      }
    };
  }

  @Override
  public int getPort() {
    throw new UnsupportedOperationException("Unsupported operation getPort()");
  }

  @Override
  public int getReceiveBufferSize() throws SocketException {
    try {
      return localSocket.getReceiveBufferSize();
    } catch (IOException e) {
      throw toSocketException(e);
    }
  }

  @Override
  public SocketAddress getRemoteSocketAddress() {
    return new SocketAddress() {};
  }

  @Override
  public boolean getReuseAddress() {

View on GitHub (pinned to 64daddc1f3)

Solutions

Stop calling getPort() on UdsSocket; a Unix domain socket has no port — derive endpoint info from the socket file path instead
Guard socket introspection code with an instanceof/UDS check before querying port-related options
If port info is genuinely needed, use a TCP (host:port) gRPC target rather than the UDS transport

Example fix

// before
int port = socket.getPort();
// after
if (socket instanceof io.grpc.android.UdsSocket) {
  // Unix domain socket: no port; use the socket path instead
} else {
  int port = socket.getPort();
}

Defensive patterns

Strategy: try-catch

Validate before calling

boolean hasPort = !(socket instanceof io.grpc.android.UdsSocket);

Type guard

static boolean supportsPort(java.net.Socket s) { return !(s instanceof io.grpc.android.UdsSocket); }

Try / catch

try { port = socket.getPort(); } catch (UnsupportedOperationException e) { port = -1; }

Prevention

Treat UdsSocket as a portless transport: never query port-related Socket accessors on it
Centralize socket introspection behind a helper that checks for UDS first
When switching gRPC targets from host:port to 'uds:', audit any code reading socket endpoints

When it happens

Trigger: Any code path that calls UdsSocket.getPort() directly, or library/framework code that introspects the socket (e.g. channel factories, socket diagnostics, connection logging) and asks for the remote/local port.

Common situations: Developers treating the UDS channel like a TCP channel; middleware or debug tooling that logs socket endpoints; migrating code from a TCP gRPC channel to a 'uds:' target without removing port-related socket inspection.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of grpc/grpc-java@64daddc1f3 (2026-09-08). Data as JSON: /api/errors/f026ed3062be17ae. Report an issue: GitHub.