C ++ UDP套接字端口多路复用 [英] C++ UDP Socket port multiplexing

问题描述

如何在C ++中创建客户端UDP套接字，以便它可以在另一个应用程序正在监听的端口上进行监听?换句话说，如何在C ++中应用端口多路复用?

How can I create a client UDP socket in C++ so that it can listen on a port which is being listened to by another application? In other words, how can I apply port multiplexing in C++?

推荐答案

我只想在一个端口上收听

I want to listen on only one port

您可以使用嗅探器进行此操作.只需忽略来自不同端口的数据包即可.

You can do that with a sniffer. Just ignore the packets from different ports.

我可能需要阻止它发送某些特定的数据包，因为我的程序将发送它而不是原始应用程序

I might need to stop it from sending out some particular packets, because my program will send it instead of the original application

好的，在这里，我建议您丢弃嗅探器，并使用 MITM 技术.

Okay, here I suggest you to discard sniffers, and use a MITM technique.

您需要依靠PREROUTING防火墙规则将数据包转移到"代理"应用程序.假设UDP，Linux，iptables和"代理"在同一主机上运行，​​则实际上是"代理"要做的事情:

You'll need to rely on a PREROUTING firewall rule to divert the packets to a "proxy" application. Assuming UDP, Linux, iptables, and the "proxy" running on the same host, here's what the "proxy" actually needs to do:

1..将防火墙规则添加到转移数据包中(如果需要，请手动执行):

1. Add the firewall rule to divert the packets (do it manually, if you prefer):

iptables -t nat -A PREROUTING -i <iface> -p <proto> --dport <dport>
    -j REDIRECT --to-port <newport>

2.绑定并收听<newport>.

3..中继2个端点(客户端和原始目的地)之间的所有流量.如果要在其他主机上运行"代理"，请使用

3. Relay all the traffic between the 2 endpoints (client, and original destination). If you're running the "proxy" on a different host, use getsockopt with SO_ORIGINAL_DST to retrieve the original destination address.

这听起来可能很棘手，但是...是的，因为那有点棘手:-) 如果我的假设有所不同，请查阅您的防火墙文档.

It might sound tricky, but... yeah, that's because it's a bit tricky :-) Consult your firewall documentation if my assumption diverges.

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