Iptables doesn't work

Question

Hello in virtualbox I installed Debian 8 and my web application which is running on port 8000. Virtualbox network I have in network settings bridged adapter and I can connect there via ssh from my computer. Virtualbox have ip address: 192.168.88.65 My computer have ip address: 192.168.88.51 It is in one site.

I would like have access to my web app from my computer on port 8000. But when I run nmap on my computer I see only this ports:

Nmap scan report for test (192.168.88.65)
Host is up (0.0023s latency).
Not shown: 998 closed ports
PORT     STATE SERVICE
111/tcp  open  rpcbind
3306/tcp open  mysql

but in virtualbox computer it is:

Nmap scan report for localhost (127.0.0.1)
Host is up (0.0000030s latency).
Other addresses for localhost (not scanned): 127.0.0.1
Not shown: 996 closed ports
PORT     STATE SERVICE
25/tcp   open  smtp
111/tcp  open  rpcbind
3306/tcp open  mysql
8000/tcp open  http-alt

How can I see the port 8000 from my computer??

I am trying run this commands in virtualbox but it doesn't work:

root @ debian /root ### iptables -I INPUT -p tcp --dport 8000 -j ACCEPT
root @ debian /root ### iptables-save

# Generated by iptables-save v1.4.21 on Mon Mar  6 10:11:58 2017
*filter
:INPUT ACCEPT [57:123601]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [44:124193]
-A INPUT -p tcp -m tcp --dport 8000 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8000 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8000 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8000 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8000 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 8000 --tcp-flags FIN,SYN,RST,ACK SYN -j ACCEPT
COMMIT
# Completed on Mon Mar  6 10:11:58 2017

Answer 1

The iptables rules you inserted are redundant because as the output of your iptables-save command shows, the INPUT policy is ACCEPT, so any connection will be allowed.

I could be wrong but my suspicion is that since you are using a bridged adaptor, it is subject to firewall rules on your host machine, and is not allowing you to reach your target port.

Unless you absolutely need a bridged adapter inside of your VM, I would recommend switching to NAT and simply using the port forwarding capability of VirtualBox.

Under Settings > Network > Adapter 1

Change the field "Attached To" to NAT.

Under "Advanced", hit the "Port Forwarding" button and add an entry:

Name: http (or any name you want)
Protocol: TCP
Host IP: (blank)
Host Port: 8888 (or any port you want)
Guest IP: (blank)
Guest Port: 8000 (match your web app port)

You can then start your VM (guest) and then from your host computer, open a browser and access your web app by going to endpoint below (appending any path you may need).

localhost:8888

For convenience, if your host machine is UNIX based, you can add a line to /etc/hosts like this:

127.0.0.1 myapp.com

Then you can use:

myapp.com:8888