6.10 Network apps

mozilla &

(in X terminal) Run the mozilla web browser. The current version is Mozilla 1.0.1 (Oct. 2002), and it is very nice. Mozilla is a descendant of netscape (netscape is on older Linux systems). Good alternatives are also konqueror and galeon (type konqueror& or galeon& in your Xterminal).

mozilla -display host:0.0 &

(in X terminal) Run mozilla on the current machine and direct the output to machine named "host" display 0 screen 0. Your current machine must have a permission to display on the machine "host" (typically given by executing the command xhost current_machine_name in the xterminal of the machine host. Other X-windows program can be run remotely the same way.

lynx file.html

View an html file or browse the net from the text mode. Although lynx's look or convenience of use is not as great as GUI-based browser, it is light-weight, almost always works, and does not require any configuration, as long as your networks is functional.

konqueror &

(in X terminal) File manager and web browser in one. Very nice, in many very competitive to mozilla. Comes with KDE.

pine

A good, old-fashioned, text-mode mail reader. Another old-fashioned and standard one is elm. Your mozilla mail will read the mail from your Internet account. pine will let you read the "local" mail, e.g. the mail your son or a cron process sends to you from a computer on your home network. The command mail could also be used for reading/composing mail, but it would be inconvenient--it is meant to be used in scripts for automation.

mutt

A really basic but extremely useful and fast mail reader.

mail

A basic operating system tool for e-mail. Look at the previous commands for a better e-mail reader. mail is good if you wanted to send an e-mail from a shell script.

kmail &

(in X-terminal) Nice, GUI mail program. I use kmail, it is much better than netscape mail. I can have multiple accounts and retrieve mail from the smtp (local) server and pop3 servers (internet service provider) to the same mailbox. Simple and elegant. Supports digital signatures.

licq &

(in X terminal) An icq "instant messaging" client. Another good one is kxicq. Older distributions don't have an icq client installed, you may have to do download one and install it.

knode &

(in X terminal) Start my favourite newsgroup (usenet) reader. It is MUCH better than the netscape's built-in reader.

talk username1

Talk to another user currently logged on your machine (or use "talkusername1@machinename" to talk to a user on a different computer) . To accept the invitation to the conversation, type the command "talk username2". If somebody is trying to talk to you and it disrupts your work, your may use the command "mesg n" to refuse accepting messages. You may want to use "who" or "rwho" to determine the users who are currently logged-in. talk is one of the old-fashioned "standard" UNIX tools, yet it still can be cool and useful in some situations.

telnet server

Connect to another machine using the TELNET protocol. Use a remote machine name or IP address. You will be prompted for your login name and password--you must have an account on the remote machine to login. Telnet will connect you to another machine and let you operate on it as if you were sitting at its keyboard (almost). Telnet is not very secure--everything you type moves through the networks in open text, even your password! A competent system administrator on a computer "on-route" can read what you type. Use ssh (requires some setup) for encrypted transmission.

rlogin server

(=remote login) Connect to another machine. The login name/password from your current session is used; if it fails you are prompted for a password.

rsh server

(=remote shell) Yet another way to connect to a remote machine. The login name/password from your current session is used; if it fails you are prompted for a password.

ssh servername -l username

(=secure shell) Connect to a server (remote login) using a secure connection. ssh is secure because encrypts all the data transfered over the network using a pair of RSA"public-private" keys. If you don't specify the username, your current user name is assumed.

Both the client and the server must have ssh service (daemon) running. They are normally available on newer Linux distributions (e.g., RH7.0). Before using ssh, some setup may be necessary. The user creates his/her RSA key pair (for encryption) by running the command ssh-keygen. This stores the private key in the file $HOME/.ssh/identity and the public key in $HOME/.ssh/identity.pub in the user's home directory. To allow automatic login, the user should copy the identity.pub to $HOME/.ssh/authorized_keys in his/her home directory on the remote machine After this, the user can log in without giving the password. The most convenient way to use RSA authentication may be with an authentication agent. See man 1 ssh-agent for more information. If automatic authentication methods fail, ssh prompts the user for a password. The password is sent to the remote host for checking; however, since all communications are encrypted, the password cannot be seen by someone listening on the network.

From: Benjamin Smith <bens@benjamindsmith.com> (edited for space):

I recently got openssh 2.9.2p1 up and running, along with the password-free login option. It took some doing and none of the howtos covered this. Would you like the "magic tidbit" that makes it all work? Here it is: "the default is to SSH2 and DSA keys, which you generate with 'ssh-keygen -d' and it goes into ~/.ssh/id_dsa.pub, which you would copy to remotehost:.ssh/authorized_keys2" Use this instead of the usual "authorized_keys" file given in the howtos, and VOILA! It actually works.


ftp server

Ftp another machine. (There is also ncftp which adds extra features and gftp for GUI .) Ftp is good for copying files to/from a remote machine. Try user "anonymous" if you don't have an account on the remote server. After connection, use "?" to see the list of available ftp commands. The essential ftp commands are: ls (see the files on the remote system), ASCII,binary (set the file transfer mode to either text or binary, important that you select the proper one ), get (copy a file from the remote system to the local system), mget (get many files at once), put (copy a file from the local system to the remote system), mput (put many files at once), bye (disconnect). For automation in a script, you may want to use ncftpput and ncftpget, for example:

ncftpput -u my_user_name -p my_password -a remote.host.domain remote_dir *local.html

"ncftp" seems to have a problem if your computer is behind a firewall--you need to configure the file /home/usr_name/.ncftp/firewall. Alternatively, you may use "lftp" to accomplish the same, for example:

lftp -e "mput -a *local.html" -u my_user_name,my_password ftp://remote.host.domain

For keeping mirrors of ftp directories, one can use fmirror

wget -m --no-parent http://sunsite.dk/linux-newbie

Copy files from web sites. The example above uses the option -m (=mirror) to retrieve a complete set of files from the master site of this guide. The option "--no-parent" limits the retrieval to the files in the given directory and its subdirectories.

minicom

Minicom program for serial port "terminal emulation". Looks and works like "Procomm" or "Telix". It is useful for testing and debugging your serial communication.

rx

Receive files using the Zmodem, Ymodem, or Xmodem protocol. Xmodem requires a filename. Use rx --help for more info. Who uses these protocols any more anyway?

"I use Zmodem regularly. I have two computers running (SuSE) Linux, a laptop and a desktop. The desktop computer does not have access to an internet connection. So, in order to get files I downloaded from one computer to the other, I send them over via a null-modem cable, using Minicom and the Zmodem protocol. This way I can even connect my laptop from work running Win2000 to my Linux machine using Reflexion (a win32 terminal emulation prog)" (from Berry Vos, B.Vos@getronics.com, 2001 08 28).



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