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公共网络服务器与NAT后的服务器之间的双向通信解决方案

[英]Solution for 2-way communcation between public network server and servers behind NATs

原文 2016-06-21 02:41:07 0 1 java/ nat

I have below scenario and would like to find a solution for it: 我有以下情况，并希望找到解决方案：

Private Server A is behind NAT, it has no fixed public IP address. 专用服务器A位于NAT之后，它没有固定的公用IP地址。

Public Server B has public IP. 公用服务器B具有公用IP。

Public Server B will need to send messages to private server A consequently upon business requirements. 因此，根据业务需求，公共服务器B将需要向私有服务器A发送消息。

I am wonder whether there is any Java solution for this kind of communication? 我想知道是否有用于此类通信的Java解决方案？

Since private server A has no fixed IP address, it will has to first has a way to tell public server B its IP/Port, etc, or start a connection like websocket first. 由于私有服务器A没有固定的IP地址，因此它首先必须具有一种方法来告知公共服务器B其IP /端口等，或者首先启动类似websocket的连接。 Then keep the connection long alive, then public server B can send data back to server A. 然后使连接保持活动状态，然后公共服务器B可以将数据发送回服务器A。

This scenario is similar but not exactly the same as UDP hole punching. 这种情况与UDP打孔相似但不完全相同。 Since I am new to Java, I am wondering whether there is any existing Java lib for such case? 由于我是Java新手，所以我想知道是否存在针对这种情况的现有Java库？

The restrictions are: 限制是：

We are not allowed to configure the NAT network, which means port forwarding are not applicable. 我们不允许配置NAT网络，这意味着端口转发不适用。
There will be many NATs. 将会有许多NAT。 Inside each NAT there will be a server(Or a cluster) communicating to the public server. 在每个NAT内，将有一个服务器（或群集）与公用服务器通信。 So websocket solution may not a best solution as it will keep the public server maintaining many connections in memory. 因此，websocket解决方案可能不是最佳解决方案，因为它将使公共服务器保持内存中的许多连接。

Thanks 谢谢

1 个解决方案

The NAT configuration basically forces you to make connections from server A, which is located behind a NAT, to server B. If you do not want to keep a connection open, then server A needs to poll periodically for information, then disconnect. NAT配置基本上会迫使您从位于NAT后面的服务器A到服务器B建立连接。如果您不想保持连接打开，则服务器A需要定期轮询以获取信息，然后断开连接。 This obviously introduces latency; 显然，这会导致延迟。 server A is disconnected for most of the period and only receives updates after it connects. 服务器A在大部分时间内都断开连接，并且仅在连接后才接收更新。

I would be surprised if you have so many servers that you cannot keep a socket connection open. 如果您有如此多的服务器而无法保持套接字连接打开，我会感到惊讶。

Java is a side issue. Java是附带问题。 Any kind of socket or websocket you would open in Java has direct analogues in other languages. 您将用Java打开的任何套接字或websocket都具有其他语言的直接类似物。