How to open a port on linux (Debian jessie)
I have a process that I'm running on my local machine which is listening on TCP port 9000. I would like to consume on another computer of my network. Here is my configuration:
I would like to see it when I run nmap 10.18.12.12 but I don't know how.
nmap localhost Starting Nmap 6.47 ( http://nmap.org ) at 2015-08-20 13:49 ART Nmap scan report for localhost (127.0.0.1) Host is up (0.00037s latency). Other addresses for localhost (not scanned): 127.0.0.1 Not shown: 987 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 25/tcp open smtp 80/tcp open http 111/tcp open rpcbind 443/tcp open https 631/tcp open ipp 3306/tcp open mysql 5432/tcp open postgresql 8000/tcp open http-alt **9000/tcp open cslistener** 9001/tcp open tor-orport 9999/tcp open abyss
Starting Nmap 6.47 ( http://nmap.org ) at 2015-08-20 13:45 ART Nmap scan report for 10.18.12.12 Host is up (0.00073s latency). Not shown: 994 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 80/tcp open http 111/tcp open rpcbind 443/tcp open https 3306/tcp open mysql
Answer
The service is bound to 127.0.0.1. You can see this without using Nmap; use netstat instead: netstat -tln will show all listening TCP ports. You should see something like this:
$ netstat -tln Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN
In this example, the service on port 21 (FTP) is listening on the special address 0.0.0.0 which means "any available address," but the service on port 9000 is bound to 127.0.0.1, which is a special address ("localhost" or "loopback") not accessible from the network.
Most services will have a way to specify which addresses or interfaces to listen on. Read the manual for the service you are interested in to determine how to change this.