beginner backend web programming questions about SSH

So, I've taken a handful of programming courses(object-oriented, web) but never h开发者_运维知识库ad "hands-on" projects where it's outside of coding.

Now I'm trying to figure out what these SSH stuff is about, I can't even figure out which client to use, so picked filezilla for now.

My question is, where can I read more about these terms like ports, and whatnots, in a way so I'm not learning aimlessly.

Thanks!

Basically, SSH is a way to command another computer exactly what to do over the Internet. You can execute any commend the remote system has, and your user has permission for.

The Internet

The Internet runs on a series of protocols collectively named TCP/IP. TCP/IP defines a way to find and address individual computers (IP) and a way to communicate between them (TCP).

You can think of computers on the Internet as a large collection of office buildings all close together. Each office has the exact same number of windows: 65535. Offices (computers) communicate by stringing channels between windows (ports). Each channel has two ends, called sockets. Each socket is associated with a port on the respective computer. We send data back and forth, and then the connection is closed.

Client/Server

There are two types of computers on the Internet: clients, and servers. Clients request information, and servers provide it. Ports 1-1024 are reserved for servers, 1 port per protocol. The full list is here, and as you can see, it is not without contention.

Let's say you visit a website

Your browser, the client program, sees that you typed "stackoverflow.com", and using DNS, discovers that stackoverflow.com is computer number 64.34.119.12. This is it's IP address. It allows your computer to find the network stackoverflow.com is located in, route to it, and establish a connection to the Stack Overflow web server. The web server is a program that accepts client requests from a browser like yours.

They speak in a protocol called HTTP - it allows your browser to request a page determined by a URL. The server sees the request, runs a program to construct a web page (or retrieves an HTML file, image, or any other file), and sends the result back to the browser. Port 80 has been reserved for HTTP. That means, your computer chooses a random port to connect from, and connects to port #80 on the server.

Unix and the shell

The majority of the Web (The Internet, even) runs on an OS called Linux (a Unix variant), instead of something like Windows. Unix systems possess a command-line interface, running a program called a "shell", which is a direct interface to the system. The shell accepts input, one command at a time. You type text in, and it spits out the out put of the command.

Secure Shell

SSH allows you to do this securely. All data traffic is encrypted using a well-studied published "public-key" cryptographic system. (In fact, it was major news when a vulnerability was discovered in a supporting encryption scheme, see these advisories).

SSH is a protocol commonly running on port 22. Anyone with a computer on the Internet (not behind a firewall) can run an SSH server, and allow users to connect to it and execute commands.

The majority of systems administrators and software developers using Unix on the server use SSH to configure, control, and upload programs to that server (located in some data center somewhere).

More

There are many many more details to all of this. Any term or acronym above can be typed into Wikipedia for pretty comprehensive information. There are plenty of books on Unix, Networking, and Web programming.

SSH is originally a secured replacement for telnet. The need for SSH arose from the fact that telnet does not support encryption and therefore everything (commands, output and password) was plainly visible on the network for all to see.

Because in the beginning SSH encryption (based on key exchange) was supposed to be strong (and it was indeed a marked improvement), and was open source, it took off rapidly and several extensions to the protocol were added, especially in the domain of remote file manageent and transfer. In addition, SSH is used in tunelling and port forwarding configurations.

In the domain of file copy there are several options.

1. SCP: cp (copy). Inspired by rcp, an early file transfer extension to ssh.
2. SFTP: SSH File Transfer Protocol, a newer SSH extension to support File copy and browsing (but not really like FTP with 2 ports). It is more feature rich than both scp and ftp. Think of it as a remote file system protocol (however, however somewhat slower than scp).
3. FTPS: FTP over TLS/SSL. Needs 2 ports like ftp, one for command and one for data. Both connections can be encrypted.
4. Secure FTP. Real FTP tunelled over SSH.

The site to which you will need to connect probably offers SFTP. You just need to declare the remote server connection configuration in Filezilla site manager. You will need to provide the server ip address or name, the SSH server port, usually 22 but there are other possibilities (you should have been provided with this info) and select sftp as server type). When the connection is established, accept the public key and that should be it.

You can then drop your devs on the remote server.

OS choice
You shall first make a kind of choice between 2 worlds (MS or Linux). Provided that the Linux community is somehow significantly less reluctant to share explanations. Also you will loose less time by choosing one or the other one, avoiding to wonder the same questions twice, with different answers depending on which OS you chose.

I experienced both, starting to search for solutions in the MS world, that I knew. Big mistake, loss of time. Then I changed, too late, to the Linux world. So I would advice to go straight to the linux OS for learning. Really many distributions for this. I would advice Debian (opened, user friendly, simple, safe, huge community) but you'll get as many proposals as there are admin.

OS understanding
http://www.linuxfromscratch.org/lfs/
http://www.ibm.com/developerworks/library/l-bash.html
http://tldp.org/LDP/abs/html/

Specific Questions about SSH
It depends a lot on the system you will choose but you could easily build a small client and a small server, then configure both and use ssh. Your 2 servers could even be hosted on the same machine, locally if you wish. Then you will learn how to set up the ssh-client side (often called ssh_config) and the ssh server side (often named sshd_config, with "d" standing for daemon).

Here you can find explanations about ssh for both worlds :
http://support.suso.com/supki/SSH_Tutorial_for_Linux

Some keywords for your google searches
List_of_TCP_and_UDP_port_numbers
ssh-keygen : encrypted keys (private/public),
ssh-add ssh agent
Gentoo keychain

and later but soon if you administrate your server on your own
The two main ones :
1) iptables
You may start with this and then go further with that one

2) fail2ban
this is a complement tool for which you'll find easily plenty of docs ...

Have fun :-)

EDIT: you can easily experience a Linux machine hosted in a windows OS, using virtualization (virtualbox, vm-ware..). It's a safe start and offer a good payback for this time investment. It would allow you to host as many machines (for example one linux server and one linux client) as you wish, in the limits of your HD room.

I assume you need to learn shell scripting. I recommend this book.
Filezilla is a FTP client. Try Putty - free SSH Client. And of course you need Linux server.

If you want to learn about SSH in depth then may I advise you this book SSH: The Secure Shell The Definitive Guide

See here for more info: http://www.snailbook.com/

I've read the book and learned really a lot. It teaches you all about setting up servers, clients, key agents and various (practical) applications.