P2P内网透传的UDP协议代码实现，U_Trans需运行在有公网的IP设备上。U_ServerA为内网1(如办公室局域网且可以上网)，U_ClientB为内网2(如出差宾馆局域网且可以上网)。U_ServerA、U_ClientB内网均没有在对应路由设置直接映射关系，不可以直接互通数据。U_Trans负责将U_ServerA、U_ClientB互联，类似代理。(P2P internal network transmissions UDP protocol code implementation, U_Trans need to run on the public network of IP devices. U_ServerA is an intranet 1 (such as an office LAN and can be online), and U_ClientB is an intranet 2 (such as a business trip to a hotel LAN and can surf the Internet). U_ServerA and U_ClientB intranet have no direct mapping relations in the corresponding routing settings, and can not communicate directly with the data. U_Trans is responsible for interconnecting U_ServerA, U_ClientB, as a proxy.)