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)
```

	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{

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())

	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
	}

	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
	}))

				fmt.Println("muxServer: Mux", m.ID, "send EOF", hErr)
			}
			msg.Flags |= FlagEOF
			if hErr != nil {
				msg.Flags |= FlagPayloadIsErr
				msg.Payload = []byte(*hErr)
			}
			msg.setZeroPayloadFlag()
			m.send(msg)
			return
		}
		msg.Payload = payload
		msg.setZeroPayloadFlag()
		m.send(msg)
	}
}

// handleRequests will handle the requests from the client and call the handler function.

}

// Post submit 'payload' to specified URL
func (c Config) Post(reqURL string, payload any) (string, error) {
	if !c.Registered() {
		return "", errors.New("Deployment is not registered with SUBNET. Please register the deployment via 'mc license register ALIAS'")
	}
	body, err := json.Marshal(payload)
	if err != nil {
		return "", err
	}

		}
	}
	payload := make([]byte, 1, plSize)
	payload[0] = xlMetaInlineDataVer
	payload = msgp.AppendMapHeader(payload, uint32(len(keys)))
	for i := range keys {
		payload = msgp.AppendStringFromBytes(payload, keys[i])
		payload = msgp.AppendBytes(payload, vals[i])
	}
	*x = payload
}

// entries returns the number of entries in the data.

    assert response.json() == {"detail": "Not authenticated"}


def test_security_http_basic_non_basic_credentials():
    payload = b64encode(b"johnsecret").decode("ascii")
    auth_header = f"Basic {payload}"
    response = client.get("/users/me", headers={"Authorization": auth_header})
    assert response.status_code == 401, response.text