How to open a port?
I have ubuntu 12.04 and I'm not able to allow certain port in my firewall. So I basically said I will allow everything but it's still not working. Please help. nmap on this machine from other machine says:
$ nmap host_name
Not shown: 996 closed ports
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
139/tcp open netbios-ssn
445/tcp open microsoft-ds
and here is nmap from the same machine
$ nmap localhost
Starting Nmap 5.21 ( http://nmap.org ) at 2014-01-21 11:14 PST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000080s latency).
Not shown: 991 closed ports
PORT STATE SERVICE
22/tcp open ssh
25/tcp open smtp
53/tcp open domain
80/tcp open http
139/tcp open netbios-ssn
445/tcp open microsoft-ds
631/tcp open ipp
3306/tcp open mysql
8000/tcp open http-alt
Nmap done: 1 IP address (1 host up) scanned in 0.04 seconds
I want to open port 8000 and here is the output of iptables.
# iptables -L -n
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
mmoghimi@titan:~$ sudo netstat -tulpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN 14842/mysqld
tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 982/smbd
tcp 0 0 127.0.0.1:39346 0.0.0.0:* LISTEN 3405/GoogleTalkPlug
tcp 0 0 127.0.0.1:50995 0.0.0.0:* LISTEN 3405/GoogleTalkPlug
tcp 0 0 127.0.0.1:5939 0.0.0.0:* LISTEN 2412/teamviewerd
tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 2429/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 985/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1267/cupsd
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1748/exim4
tcp 0 0 0.0.0.0:17500 0.0.0.0:* LISTEN 2885/dropbox
tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN 982/smbd
tcp 0 0 127.0.0.1:8000 0.0.0.0:* LISTEN 4134/python
tcp6 0 0 :::139 :::* LISTEN 982/smbd
tcp6 0 0 :::80 :::* LISTEN 1832/apache2
tcp6 0 0 :::22 :::* LISTEN 985/sshd
tcp6 0 0 ::1:631 :::* LISTEN 1267/cupsd
tcp6 0 0 ::1:25 :::* LISTEN 1748/exim4
tcp6 0 0 :::445 :::* LISTEN 982/smbd
udp 0 0 127.0.0.1:53 0.0.0.0:* 2429/dnsmasq
udp 0 0 0.0.0.0:68 0.0.0.0:* 2403/dhclient
udp 0 0 128.54.44.214:123 0.0.0.0:* 3430/ntpd
udp 0 0 MYIP:123 0.0.0.0:* 3430/ntpd
udp 0 0 127.0.0.1:123 0.0.0.0:* 3430/ntpd
udp 0 0 0.0.0.0:123 0.0.0.0:* 3430/ntpd
udp 0 0 137.110.255.255:137 0.0.0.0:* 2602/nmbd
udp 0 0 MYIP:137 0.0.0.0:* 2602/nmbd
udp 0 0 128.54.47.255:137 0.0.0.0:* 2602/nmbd
udp 0 0 128.54.44.214:137 0.0.0.0:* 2602/nmbd
udp 0 0 0.0.0.0:137 0.0.0.0:* 2602/nmbd
udp 0 0 137.110.255.255:138 0.0.0.0:* 2602/nmbd
udp 0 0 MYIP:138 0.0.0.0:* 2602/nmbd
udp 0 0 128.54.47.255:138 0.0.0.0:* 2602/nmbd
udp 0 0 128.54.44.214:138 0.0.0.0:* 2602/nmbd
udp 0 0 0.0.0.0:138 0.0.0.0:* 2602/nmbd
udp 0 0 0.0.0.0:17500 0.0.0.0:* 2885/dropbox
udp 0 0 0.0.0.0:36889 0.0.0.0:* 1356/avahi-daemon:
udp 0 0 0.0.0.0:5353 0.0.0.0:* 1356/avahi-daemon:
udp6 0 0 ::1:123 :::* 3430/ntpd
udp6 0 0 fe80::fab1:56ff:fe9:123 :::* 3430/ntpd
udp6 0 0 fe80::3e77:e6ff:fe6:123 :::* 3430/ntpd
udp6 0 0 :::123 :::* 3430/ntpd
udp6 0 0 :::33792 :::* 1356/avahi-daemon:
udp6 0 0 :::5353 :::* 1356/avahi-daemon:
Your iptables output shows that no port is blocked.
So the question is: Is anything listening on port 8000? If nothing is listening on a port but the port is not blocked by a firewall nmap will report it as closed. From here:
closed
A closed port is accessible (it receives and responds to Nmap probe packets), but there is no application listening on it. They can be helpful in showing that a host is up on an IP address (host discovery, or ping scanning), and as part of OS detection. Because closed ports are reachable, it may be worth scanning later in case some open up. Administrators may want to consider blocking such ports with a firewall. Then they would appear in the filtered state, discussed next.
So the nmap report: "996 closed ports" actually say that those ports are not blocked by a firewall but no program is listening on them. nmap reports a blocked port as filtered:
filtered
Nmap cannot determine whether the port is open because packet filtering prevents its probes from reaching the port. The filtering could be from a dedicated firewall device, router rules, or host-based firewall software. ...
So if you put an application in listening state on port 8000 it will likely show up in the output of nmap. You can do this if you just run python3 -m http.server or python -m SimpleHTTPServer on the machine on which you are trying to open the ports, this will put a HTTP server listening on port 8000. Then run nmap again to scan the machine.
UPDATE:
Your netstat output has this line:
tcp 0 0 127.0.0.1:8000 0.0.0.0:* LISTEN 4134/python
That means your python program is only listening on localhost (127.0.0.1), so it is only accessible from localhost, not from outside. The program has to listen on the IP of your network adapter or on the universal 0.0.0.0 IP. The problem is what I wrote above, no program is listening on the 8000 port (from the outside world) so nmap says it is closed.
To Enable Port In Ubuntu
sudo ufw allow <port_nr>
e.g to allow ssh
sudo ufw allow 22
sudo ufw enable
Thats IT