Research And Implementation Of Embedded TCP/IP Protocol Stack

LwIP is a set of open source embedded TCP/IP protocol stack developed and maintained by Swiss Academy of Sciences. LwIP is characterized by saving memory resources, and in general it requires only tens of KB of RAM and 40KB of ROM. This makes LwIP protocol stack suitable for use in low-end embedded system. Howerver, LwIP does not implement TCP/IP protocol completely.NAPT(Network Address Port Translation) feature is a good example,which can make internal IP addresses share an public IP to access external network.Porting LwIP to embedded real-time operating system based on uC/OS-II and S3C44B0X processor and NAPT feature implementation on LwIP are studied in this paper.First, the paper describes the TCP/IP protocols,including IP protocol, TCP protocol, UDP protocol, ICMP and ARP protocol. Then Principle of LwIP's IP layer, UDP layer and TCP layer are analyzed. Then LwIP application system model is designed, and overall system is planned; Second, uC/OS-II is ported to S3C44B0X processor to lay the foundation of LwIP application; Third, LwIP is ported to the platform ready, so LwIP's operating system emulation layer and network layer is fully studied. Fourth, a detailed analysis of the interface between NAPT feature and original LwIP is made. Then input and output functions of NAPT are fully designed and realized. Finally, Porting of uC/OS-II to S3C44B0X, Porting of LwIP to uC/OS-II and NAPT feature on LwIP are tested.