如何将端口从一台机器转发到另一台机器？

Question

考虑以下情况：

在我家里，我有一个路由器（连接到互联网）、服务器（S）和我的主机（M）。S 可从 Internet 访问（它具有静态 IP），并且 24/7 全天候运行，而 M 则不然。

有时，我想让一些应用程序（它侦听 M 上的某个端口，例如 8888）可以从外部 Internet 访问。

为此，我想在 S (2222) 上设置一些端口以转发到 M 的端口 8888，以便任何访问 S:2222 的人都感觉他正在访问 M:8888。

我尝试使用 ssh 端口转发，我最好的尝试如下：

ssh -L 2222:M:8888 -N M

但这仅允许我从服务器本身访问 2222 端口，而不能从其他机器访问。

Is there some way to do it properly? Preferably, I'd like it to be a simple command, which I would be able to start and shut down with ^C when I don't need that forwarding anymore.

Answer 1

Yes, this is called GatewayPorts in SSH. An excerpt from ssh_config(5):

GatewayPorts
        Specifies whether remote hosts are allowed to connect to local
        forwarded ports.  By default, ssh(1) binds local port forwardings
        to the loopback address.  This prevents other remote hosts from
        connecting to forwarded ports.  GatewayPorts can be used to spec?
        ify that ssh should bind local port forwardings to the wildcard
        address, thus allowing remote hosts to connect to forwarded
        ports.  The argument must be “yes” or “no”.  The default is “no”.

And you can use localhost instead of M in the forwarding, as you're forwarding to the same machine as you're SSH-ing to -- if I understand your question correctly.

So, the command will become this:

ssh -L 2222:localhost:8888 -N -o GatewayPorts=yes hostname-of-M

and will look like this in netstat -nltp:

tcp        0      0    0.0.0.0:2222   0.0.0.0:*  LISTEN  5113/ssh

Now anyone accessing this machine at port 2222 TCP will actually talk to localhost:8888 as seen in machine M. Note that this is not the same as plain forwarding to port 8888 of M.

Answer 2

还有另一种方法。您可以使用 iptables 设置从 S:2222 到 W:8888 的端口转发。单个命令：

iptables -t nat -A PREROUTING -p tcp --dport 2222 \
         -j DNAT --to-destination 1.2.3.4:8888

其中 1.2.3.4 是 M 的 IP 地址。它被称为 NAT（网络地址转换）。

Answer 3

更多选择：（netcat传统）或socat

在服务器 (S) 上：

socat tcp-listen:2222,reuseaddr,fork tcp:M:8888

或者

nc -l -p 2222 -c 'nc M 8888'

详细信息参见： 创建从一个本地端口到另一个本地端口的隧道的简单方法？