A network-traversal method includes: receiving an address information of a network device from a link server; generating a port number sequence composed of port values according to an external port number of the address information; and sending a link packet to an external network address of the address information in an order of the port values in the port number sequence until receiving an acknowledgement packet from the network device. At least one of the port values is related to the external port number. A part of the rest port values is/are generated gradually based on the external port number, and the others of the rest port values is/are generated randomly.