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I'm going to set up a Raspberry Pi B+ without keyboard, mouse and screen. I'm only going to use PuTTy (MS-windows, ssh client) and an ethernet cable between my Raspberry Pi and my router.

Raspberry Pi's hard drive is a SD-card and on the SD-card there is a file named "cmdline". I open the file "cmdline" and added in "ip=192.168.1.2" to sett the IP address on the Raspberry Pi.

Tutorial:
https://youtu.be/Ioih6MHNNqc?t=1m1s

Then I wrote this command:

nmap -F 192.168.1.1-100

It scans all the IP adresses from 192.168.1.1 to 192.168.1.100

Then I found 192.168.1.2

Nmap scan report for 192.168.1.2
Host is up (0.0084s latency).
All 100 scanned ports on 192.168.1.2 are closed

But the ports are closed. How can I open ports? Can I do that in the file "cmdline"?

I found the answer now!

Just add a empty file named "ssh" with no extenstion such as .txt or .c. Only "ssh" in the boot folder and rootfs folder of the SD card for the Raspberry Pi.

Then go to your router and find what IP the raspberry pi is set at.

In bash type sudo apt-get install openssh-server

This will install the ssh server, it will listen on port 22, port 22 will become open. For what you have said you are trying to do, you do not need any other ports open.

To do this, you can not remote login, because ssh is the remote login tool. Therefore, do one of these.

• When you setup noobs, tell it to install ssh-server (that would be another question). According to https://raspberrypi.stackexchange.com/q/59429/17370 you need to add a file named ssh to the boot directory, by removing SD card, and using another machine (do read this other question).


• Connect SD card to another Unix box, and use it to install ssh-server (that would be another question).


• Connect a monitor and keyboard to the pi (temporarily), and type the command.

Also nmap only scanned 100 ports, there are many more than that
( 2¹⁶ = 65536 ). So tell nmap to scan them all (it will be slower).

You "open" a port simply by having a program listening for incoming connections on that port:

$ nc -l 12345

Poof! Port 12345 is now open and listening for incoming connections because nc is waiting for one.

A port being "closed" doesn't mean it's locked down; it simply means that there's nothing there listening for an incoming connection request.

If your question is more specifically about connecting via secure shell and not just generically establishing a connection to an arbitrary port, you need to install and start a secure shell server:

# apt install openssh-server
# service sshd start

first you need to install openssh-server on the pi.

1- plug your keyboard and your screen into it

2- boot it and open a terminal

3- download and install openssh-server deb package

 $ apt-get install openssh-server

4- enable and start sshd

 $ systemctl enable sshd
 $ systemctl start sshd

now you ll be able to ssh into the pi