grpc/grpc-java · info · UnsupportedOperationException

Unsupported operation getTrafficClass()

Error message

Unsupported operation getTrafficClass()

What it means

getTrafficClass() reads the IP_TOS/DSCP traffic-class option, which only applies to IP sockets. UdsSocket delegates to a LocalSocket over a Unix domain socket where this option does not exist, so the override throws UnsupportedOperationException.

Solutions

1. Remove traffic-class reads for UDS channels — traffic class is meaningless without IP
2. Skip this option in generic socket-option readers when the socket is a UdsSocket
3. If QoS per-traffic-class is required, route that traffic over a TCP channel instead

Example fix

// before
int tc = socket.getTrafficClass();
// after
if (!(socket instanceof io.grpc.android.UdsSocket)) {
  int tc = socket.getTrafficClass();
}

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

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

try { tc = socket.getTrafficClass(); } catch (UnsupportedOperationException e) { tc = 0; }

When it happens

Trigger: Direct call to UdsSocket.getTrafficClass(), or code that enumerates/reads all Socket options (QoS configuration, network-telemetry harnesses) on the UDS socket.

Common situations: Applying QoS/DSCP settings meant for IP networks to a UDS-based gRPC channel; generic socket-metrics tooling in an Android app using 'uds:' targets.

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

• Unsupported operation setTrafficClass()
• getChannel() not supported
• getInetAddress() not supported
• OkHttpChannelBuilder not found on the classpath
• Unsupported operation getKeepAlive()

AI-assisted analysis of grpc/grpc-java@64daddc1f3 (2026-09-08). Data as JSON: /api/errors/26e58219db1f5972. Report an issue: GitHub.

Appendix: source

Thrown at android/src/main/java/io/grpc/android/UdsSocket.java:200

  }

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

  @Override
  public boolean getTcpNoDelay() {
    return true;
  }

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

  @Override
  public boolean isBound() {
    return localSocket.isBound();
  }

  @Override
  public synchronized boolean isClosed() {
    return closed;
  }

  @Override
  public boolean isConnected() {
    return localSocket.isConnected();
  }

  @Override

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