ZeroHello said port closed but nmap says it is open

### Step 1: Please describe your environment

* ZeroNet version: Rev3844
* Operating system: Linux
* Web browser: Firefox
* Tor status: not available
* Opened port: ?
* Special configuration: Using docker

### Step 2: Describe the problem:

ZeroHello says "Your port 15441 is closed. You are still fine, but for faster experience try open it."
It always used to show 'opened' in the precedent version. And nmap says the port is open.

```
root@webradio:~# nmap localhost -p 15441

Starting Nmap 7.01 ( https://nmap.org ) at 2019-02-06 16:12 UTC
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00014s latency).
Other addresses for localhost (not scanned): ::1
PORT STATE SERVICE
15441/tcp open unknown
```

From my machine it also says open :
```
lola@HappyPills:~$ nmap **.**.**.** -p 15441

Starting Nmap 7.60 ( https://nmap.org ) at 2019-02-06 17:30 CET
Nmap scan report for 168-214-15-51.rev.cloud.scaleway.com (51.15.214.168)
Host is up (0.23s latency).

PORT STATE SERVICE
15441/tcp open unknown

Nmap done: 1 IP address (1 host up) scanned in 0.52 seconds
```

#### Steps to reproduce:

1. Run Zeronet inside docker container (using official image)
2. Open ZeroHello and verify if port open

#### Observed Results:

Message show port being close.

#### Expected Results:

ZeroHello saying it is open.

#### Notes

Running the same version on my local computer and not inside the docker and I have the port being detected open.

Start at the ZeroHello port-status check and reproduce the report inside and outside the official Docker container. Compare its result with nmap on port 15441, including the container's port exposure and the address being checked. Done means ZeroHello correctly reports the externally reachable port in the Docker setup and the mismatch has regression coverage.

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