Research on Packet Analyzing Based on Winsock Technology
基于Winsock技术的数据包解析研究

Abstract Packet analyzing is the basis of packer filtering. Analyzing packets is the most important issue which must be resolved by packet filtering firewall. There are many types of protocols to construct packets. It should manipulate packets according to the protocol used. It has to comprehend exactly packets, control them, and implement packet filtering at last. Winsock SPI breaks the transparence of services at the bottom, and provides the possibility to modify the SPI service connection. It can implement packer filtering easily. Concretely, we can append self-defined functions to control communications of packets. For example, it can intercept, transmit and discard packets. Of course, it can also accomplish QoS, expand the TCP/IP protocol stack, filter URL and defend the network security.