When capturing packets at the application level for the purpose of QoS monitoring, a QoS monitor needs to be bound to the same IP address and port as those of a media player. However, due to the unicast duplicate binding problem, a unicast packet captured by the QoS monitor will not be received by the media player, which means the QoS monitor have affected the operation of the media player. The present invention provides a solution to make the QoS monitor, upon the receipt of a unicast packet, forward the packet to the socket of the media player. In order to guarantee that the forwarded packet can be received by the socket of the media player, the QoS monitor needs to keep the port unchanged and replace the destination IP address with the local host address (127.0.0.1). According to the invention, the QoS monitor can sniff the media player without interference to the normal operation of the media player.