This means that the host will cease calling calling port_event() when
the port value changes.
Calling this function with a port_index and port_protocol that
does not refer to an active port subscription has no effect.
@param handle The handle field of this struct.
@param port_index The index of the port.
@param port_protocol The URID of the ui:PortProtocol.
@param features Features for this subscription.
@return 0 on success.
Unsubscribe from updates for a port.
This means that the host will cease calling calling port_event() when the port value changes.
Calling this function with a port_index and port_protocol that does not refer to an active port subscription has no effect.
@param handle The handle field of this struct. @param port_index The index of the port. @param port_protocol The URID of the ui:PortProtocol. @param features Features for this subscription. @return 0 on success.