Open ports are not visible on the host in host networking mode

[achanda]

Expected behavior

I started a server on port 8000 (python -m SimpleHTTPServer) in a container in host networking mode. I expected to see that port open in the host

Actual behavior

The port was not open on the host

Information

# docker inspect temp
...
"Networks": {
                "host": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "5ce0dfea018c15da566b920c188de7702d7e7d81178094160a2bea0b2904cefc",
                    "EndpointID": "0fcc981733e92cd656fabbbe74165adeded35ff6367b55aabbec57f6e4c30752",
                    "Gateway": "",
                    "IPAddress": "",
                    "IPPrefixLen": 0,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": ""
                }
            }
...

host# nmap -sT 127.0.0.1 -p 7000-9000

Starting Nmap 7.40 ( https://nmap.org ) at 2017-01-26 16:53 GMT
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00069s latency).
Not shown: 2000 closed ports
PORT     STATE SERVICE
7396/tcp open  unknown

Nmap done: 1 IP address (1 host up) scanned in 18.41 seconds

container# nmap -sT 127.0.0.1 -p 7000-9000

Starting Nmap 7.40 ( https://nmap.org ) at 2017-01-26 16:54 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000096s latency).
Not shown: 2000 closed ports
PORT     STATE SERVICE
8000/tcp open  http-alt

Nmap done: 1 IP address (1 host up) scanned in 0.08 seconds

Steps to reproduce the behavior

docker run -it --net="host" alpine sh
# apk add --update nmap python
# python -m SimpleHTTPServer

After this, scan 127.0.0.1 using nmap for ports between 7000 and 9000

[samoht]

Thanks for your report!

Unfortunately --net=host is not supported on Docker for Mac, as in this case the "host" involves a Linux virtual machine and an OSX host (which do not share the same network devices). What is your use-case? If you just want to open the port 8000, you can use the usual -p option without the --net option (but I guess you have an other use-case in mind).

Implement --net=host for Docker for Desktop is a big chunk of work which is not planned in the short term.

I am closing this issue as a duplicate of #1031, feel free to monitor updates on that issue if you are interested in following progress on that issue.

[niketpathak]

Any updates on this ? In 2017, host mode wasn't supported for docker for mac. Are there any evolutions as of 2020 ?

[docker-robott]

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