// Set a new payload and verify
        byte[] payload1 = "test_payload_1".getBytes();
        message.setRawPayload(payload1);
        assertArrayEquals(payload1, message.getRawPayload(), "getRawPayload should return the set payload");

        // Set another payload and verify
        byte[] payload2 = new byte[] { 1, 2, 3, 4, 5 };
        message.setRawPayload(payload2);

	b.Cleanup(grid.Cleanup)
	// Create n managers.
	for _, remote := range grid.Managers {
		// Register a single handler which echos the payload.
		errFatal(remote.RegisterSingleHandler(handlerTest, func(payload []byte) ([]byte, *RemoteErr) {
			defer PutByteBuffer(payload)
			return append(GetByteBuffer()[:0], payload...), nil
		}))
		errFatal(rpc.Register(remote, func(req *testRequest) (resp *testResponse, err *RemoteErr) {
			return &testResponse{

The server handler function has this signature: `type SingleHandlerFn func(payload []byte) ([]byte, *RemoteErr)`.

Sample handler:
```go
    handler :=  func(payload []byte) ([]byte, *grid.RemoteErr) {
        // Do something with payload
        return []byte("response"), nil
    }

    err := manager.RegisterSingleHandler(grid.HandlerDiskInfo, handler)
```

func (c *Connection) sendMsg(conn net.Conn, msg message, payload msgp.MarshalSizer) error {
	if payload != nil {
		if sz := payload.Msgsize(); cap(msg.Payload) < sz {
			PutByteBuffer(msg.Payload)
			msg.Payload = GetByteBufferCap(sz)[:0]
		}
		var err error
		msg.Payload, err = payload.MarshalMsg(msg.Payload)
		if err != nil {
			return err
		}
		defer PutByteBuffer(msg.Payload)
	}
	dst := GetByteBufferCap(msg.Msgsize())

    void testReadSecurityBuffer() {
        byte[] buf = new byte[8 + 4];
        byte[] payload = { 0x11, 0x22, 0x33, 0x44 };
        NtlmMessage.writeSecurityBuffer(buf, 0, 8, payload);
        byte[] extracted = NtlmMessage.readSecurityBuffer(buf, 0);
        assertArrayEquals(payload, extracted, "Payload should match original");
    }

    @Test
    @DisplayName("readSecurityBuffer throws when array is too short")

public interface Message {

    /**
     * Indicate that this message should retain it's raw payload
     */
    void retainPayload();

    /**
     * Determines whether to retain the message payload.
     *
     * @return whether to retain the message payload
     */
    boolean isRetainPayload();

    /**
     * Gets the raw payload of the message.
     *
     * @return the raw response message
     */

	errFatal(local.RegisterSingleHandler(handlerTest, func(payload []byte) ([]byte, *RemoteErr) {
		t.Log("1: server payload: ", len(payload), "bytes.")
		return append([]byte{}, payload...), nil
	}))
	// 2: Return as error
	errFatal(local.RegisterSingleHandler(handlerTest2, func(payload []byte) ([]byte, *RemoteErr) {
		t.Log("2: server payload: ", len(payload), "bytes.")
		err := RemoteErr(payload)
		return nil, &err
	}))

	if errCode != ErrNone {
		return cred, "", "", time.Time{}, errCode
	}

	// Payload streaming.
	payload := streamingContentSHA256
	if trailers {
		payload = streamingContentSHA256Trailer
	}

	// Payload for STREAMING signature should be 'STREAMING-AWS4-HMAC-SHA256-PAYLOAD'
	if payload != req.Header.Get(xhttp.AmzContentSha256) {
		return cred, "", "", time.Time{}, ErrContentSHA256Mismatch
	}

            response.setDigest(null);

            response.haveResponse(buffer, 1, 3);

            byte[] payload = response.getRawPayload();
            assertNotNull(payload);
            assertEquals(3, payload.length);
            assertArrayEquals(new byte[] { 2, 3, 4 }, payload);
            assertTrue(response.isReceived());
            assertFalse(response.isAsyncHandled());
        }

        @Test

            assertTrue(w.isReady(), "WriterThread should be ready to accept work");

            // Act: submit a write
            w.write(payload, 3, out);
        }

        // Assert: verify the underlying stream was called
        verify(out, timeout(1000)).write(payload, 0, 3);

        // Stop the thread by sending n = -1
        synchronized (w) {
            w.write(new byte[0], -1, out);
        }