Abstract: In order to realize remote operating for the localization grain inspection system, we researched the VPN and Winsock applied to communication software of system, the VPN can reduce the cost and difficulty of network equipment which constructs private network, Winsock can save time of developing program because it supplies the whole TCP/IP protocol. Designing communication software of remote grain monitor system based on VPN, it effectively uses congestion mode of socket and completes network state selfchecking based on multithread technique, through setting VPN client to improve the network speed, thus achieves high performance of security, reliability and speed.

Key words: Winsock, VPN, congestion mode, network state selfchecking