i'd like to load balance our lokal network printers.
From my clients i can only configure a printer manually fixed with its ip.
But i'd like to use a pdf-printer software on our network server host whenever its running. Otherwise if its turned of the printed documents should be delivered to our network attached laser printer.
I thought about something like keepalived to use for this scenario.
I know this is kinda special but has anyone did something like this before, is this possible ?
Regards Robert
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I am looking to write a program that will connect to many computers from a single computer. Sort of like "Command Center" where you can monitor all the remote system remotely on a single PC.
My plan is to have multiple Client Sockets on a form. They will connect to individual PCs remotely. So, they can request information from them to display on the Window. Remote PCs will be hosts. Is this possible?
Direct answer to your question: Yes, you can do that.
Long answer: Yes, you can do that but are you sure your design is correct? Are you sure you want to create parallel connections, one to each client? Probably you don't! If yes, then you probably want to run them in separate threads.
If you want to send some commands from time to time (and you are not doing some kind of constant video monitoring) why don't you just use one connection and 'switch' between clients?
I can't tell you more about the design because from your question is not clear about what you want to build (what exactly you are 'monitoring').
VERY IMPORTANT!
Two important notices to take into account before designing your app (both relevants only if the remote computers are not in the LAN (you connect to them via Internet)):
If the remote computers are running as servers, you will have lots of problems to explain your customers (if they are connected (and they probably are) to Internet via a router) how to setup the router and the software firewall. For example, if a remote computer is listening for commands from you, on port 1234 (for example) the firewall in the router will block BY DEFAULT any connection attempt from a 'foreign' computer (from you) to that port.
If your remote computers are running as clients, how they will know master's IP (your IP). Do you have a static IP?
What you actually need is one ServerSocket on the module running on your machine.
To which all your remote PC's will connect through their individual ClientSocket.
You can make your design other way round by putting ClientSocket on the module running on your machine and ServerSocket on the module running on remote machine.
But you will end up creating one ClientSocket to each ServerSocket, what if you have the number of remote servers increase.
Now if you still want to have multiple ClientSockets on your machine then as Altar said you could need a multi threaded application where each thread is responsible for one ClientSocket.
I would recommend Internet Direct (Indy) as they work well in threads, and you can specify a connect time-out per connection, so that your monitoring app will be able to get a 'negative' test result faster than with the default OS connect time-out.
Instead of placing them on the form, I would wrap each client in a class which runs an internal monitoring thread. More work initially but easier to keep independent from each other.
I have a headless raspberry pi with a wifi dongle and I want to use wifi two ways.
1) To make the rPI a wireless access point when there is no local wifi access point so I can connect to the rPI from my iPhone.
2) When wifi is available use the wifi dongle to do normal connection to the internet.
I think I know how to do each of these individually. It wasn't easy but I now have it connecting to my local wifi at home.
I see references to using hostapd and dnsmasq with wifi to make a local access point but they mostly assume internet connection comes from ethernet.
I'll be studying these in more detail. However I don't even know if the end goal of using the same configuration to fill both needs with one wifi dongle is even possible.
Obviously I can create two sets of config files and a script to swap them as needed but that only works if I have a connection already so I can log in.
If I add a jumper or switch to the rPI GPIO interface I could run the configuration script at startup and let it read the switch.
I might try to make the script look for an existing wifi link and go to access point mode if it doesn't find one it can access.
This would probably be a steep learning curve for me but I could probably figure it out eventually.
What I am trying to figure out now is whether I can avoid these potentially complex solutions by creating a single configuration that does both. Is a single wifi dongle sharable between these functions?
Note: I don't need it to do both at the same time. I just need the decision to be automated so it happens automatically during boot.
It is possible, although tricky to get right. (For example, what happens if you boot up, don't see an existing network for a second due to interference, then wrongly create your own network?)
Take a look at the "iwlist" command. It can scan and tell you what SSIDs (base stations) it sees. Then you can use 'grep' to see if your home network is on the list, and use that as your decision.
I'm trying to get a very old, but working great C2001A/J4100A (HP LaserJet 4) to work with the HP Linux Imaging and Printing library, but I'm having an awful time of it.
1) There's no entry in /usr/share/hplip/data/models/models.dat for [hp_laserjet_4]. This is the first problem so far when I used Bonjour discovery through an avahi.service file I put on my OpenWRT router. I don't currently have an iPhone I want it to discover with AirPrint, but this is how I started off and helps CUPS finds printers anyways.
2) SLP discovery is a complete bomb. I've traced it down to the UDP packet the JetDirect sends off in response to the broadcast discovery request. The part that is 'x-hp-p1=0' should be something like 'x-hp-p1=MFG:HP;MDL:LaserJet4;etc..' and it causes hp-probe to fail to see what printer the JetDirect is plugged into.
I can't seem to force HPLIP to bypass the bad discovery methods and it's too smart and wants to verify.
I've posted to the HPLIP help area, but they seem to run a week slow.
Instead of doing JetDirect, try LPR directly to the IP address. And any of the older PCL drivers should work against that printer.
I want to write a app which will run on different computers and need all of then to communicate with each other like "utorrent" (peer to peer). This app only will send text messages.
How can I do this? I mean sending one message to remote computer on the internet?
I have a website and every app at start can send some information to it and find information of other apps on other computers (with PHP) but I do not know how address one computer through internet and send the data directly to that. I can find the ip address with PHP but it is the ip address of router (ISP).
How a message reaches a computer? I'm wondering about addressing every computer?
My brain really stuck here, I really appreciate any help. Thanks.
In a peer-to-peer network there's no centralized server for transmitting the data from one client to another, in this case the clients must be able to act as both the server and client. This means that either you'll have to be using UPnP like most modern torrent clients, which handles port forwarding in the router, or you'll have to manually forward a port to the computer in the router.
A centralized server (like a torrent tracker) is usually used to make the clients aware of each other's existence and tell them where to connect. This is where your PHP script comes in, though PHP might not offer the most effective way of doing this, assuming you're using it in combination with a webserver to serve the data though the http protocol.
As for actual text communication, you could use the Indy socket library for that. I found this example, basically which shows how to do it: http://www.ciuly.com/delphi/indy/indy-10-client-server-basic-demo/
I'm looking for a tool under windows or mac that allows me to monitor (possibly in a simple way) the traffic going in and out of a computer of my network.
Long story short the residence where I live allows themselves to monitor the internet connection (and doesn't allow us to switch to another provider).
This annoys me on a personal level (I don't like the possibility of people checkin what I do without my knowledge as a general rule regardless of what I do) but also on a professional level (I sometimes work form home).
I'm using/trying out vpn providers (JAP, VyperVPN...) to avoid all this. it works fine with the http connections (if I run iptraces I end up in germany or US or UK ...) but I'm not sure for other applications such as online games, instant messaging softwares that use different ports.
So my question is how can I make sure that my internet traffic is using my vpn connection or not ?
Wireshark would do that for you on Windows and linux (Not sure about Mac). It uses WinPCap library and wraps in a nice UI for you to monitor the packets that you are interested. It allows you to listen to specific or all interfaces , so you can make sure your packets are going via the right interface
if you don't want them monitoring your internet usage, a vpn is a good solution, a vpn will encrypt all of your net traffic between your computer and the vpn gateway -- essentially you'd be surfing the web via a proxy and your landlords wouldnt be able to determine what you are doing.
assuming you are using a real vpn, and not just a browser based proxy solution, then the vpn should encrypt and tunnel all of your network traffic, this includes anything coming out of any port on your computer, not just http traffic.
when you install a vpn on your computer, the vpn creates a fake network device, and all of the vpn traffic gets tunneled to the vpn gateway. you can verify this by looking at your computer's routing tables. there are some vpns which allow for split traffic (split tunneling), e.g. traffic to certain domains gets tunneled through the vpn and others goes in the clear, but this is the rarity, most vpns will tunnel all of your traffic, which seems to be what you are looking for.
just make sure that your vpn uses an encryption protocol, there are some that don't -- this would defeat the whole purpose of your vpn.