Should I imagine server as a physical device like router? Or is it just a program that is on a computer? I'm confused. Please let me know. Thanks in advance
A server is a computer that provides data to other computers. It may serve data to systems on a local area network (LAN) or a wide area network (WAN) over the Internet.
Many types of servers exist, including web servers, mail servers, and file servers. Each type runs software specific to the purpose of the server. For example, a Web server may run Apache HTTP Server or Microsoft IIS, which both provide access to websites over the Internet. A mail server may run a program like Exim or iMail, which provides SMTP services for sending and receiving email. A file server might use Samba or the operating system's built-in file sharing services to share files over a network.
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i have a problem with local network connection. i'm writing an iphone application and i need to read/write files to a computer. Both devices connected on the same network.
if it's possible, i want to get connected computers ip list, select one of them and read/write files like pdf, doc, txt etc.. if it's not possible to do, i will write the computer ip which i want to connect. There is no problem, both of solution is OK.
But i dont know what do i do after get the computer's ip ?
i found this chat client/server on local, but i got it very complicated.
Anyone have any idea about this ?
You'll need to have a server running on the computer, which can show files and allow for files to be read and created.
Easiest is to run a webdav service on the computer, Apache provides the mod_dav module for this purpose.
The iPhone app then becomes the client. I'd suggest using neon for this purpose. It's a C library that provides listing, reading and writing files on a remote webdav server.
That's how I would do it.
1) Find the network address of the computer you want to connect to. For this you can make use of Bonjour. It's very easy to setup because Bonjour handles the resolving of address for you.
You just have to publish a service (e.g. _myprotocol._tcp) via the ´NSNetService` class which is available on iOS and OS X (Windows too)- in your case you would publish the service on your computer.
Then you search for the service with the NSNetServiceBrowser class.
When you found a service you can then resolve it. This actually gives you the network name of the other device.
2) Connect to the other device via a tcp socket. The CocoaAsyncSocket library is very good at this. This project also includes some examples. One example already provides a bonjour server and client implementation.
i found exactly what i want. The solution is here
It seems that both service and server refer to some web based application. But is there any precise definition of the two terms?
A server offers one or more services. Server is also a more technical term, whereas service is more a term off the problem domain.
You also need to distinguish between:
Server as hardware (see post from Dan D)
Server as software (eg. Apache HTTP server)
You can find more elaborate definiton on Wikipedia:
Service
Server
This is regardless of client-server or P2P models.
A server provides services to one or more clients, and a server(hardware) is a computer. A server(hardware) can be anything from a home computer to a big server-rack with a lot of processor power.
From the view of a computer, a server(software) is just a set of services which is available to clients on the network.
Some well known services are web-server, mail-server. ftp-server. notice they are called xxx-server because such programs consist of a client and server part. The postfix is mainly to distinguish whether we are talking about the client or the server.
So at what moment do we call something a server? We do it when a computer shares some service/content on the network, which is accessible by clients. In other words, when we make a server as defined for software.
Regarding the P2P model: every one is both a client and a server, hence called servent. The above apply to the server part of a P2P network, just remember that it also can be a client.
Futher reading:
Client-Server model
P2P
a server is a piece of hardware or on a virtual machine
a service is a process that provides services normally over the network and runs on a server
but a server can also refer to a web server which is actual a service but it's sort of like one as it hosts services
i think those are reasonable working definitions
I think a simpler way to define both besides the definition of the server being a piece of hardware, a server in the software sense is a service that serves data. In other words you interact with a server with a request and you should get a response back. It "serves" data.
A service does not need interaction and is pretty much just a random process that keeps running doing the same thing, but a server is a service because it is basically a process that keep waiting for a request to come in so that it can return a response.
"A service is a component that performs operations in the background without a user interface."
~ Android Developers
Services don't just run on servers
Shell services
Services can run from the shell. Unix refers to services as Daemons (pronounced "demons"), and Windows refers to them as services.
Client-side services
Services can run client-side. Mozilla (and other browsers) support Web Workers which run in a background thread. Client-side frameworks, like Angular, support services as well.
I need to setup a file distribution system between different sites of a WAN. Files that are dropped into some input directories on the source machine should be distributed into a directory on each of the target machines at other sites. One of the requirements is that between certain sites the only allowed traffic is SMTP. There is already a daemon in place that covers the sending side by polling input directories and mailing all found files as attachments to configured addresses (was thought for human recipients originally).
How would you design the receiving side?
One could write a stripped down SMTP server that handles only this one case, strips attachments from incoming mails, and puts them into a local directory.
One could setup a full mail server with local delivery, poll the user’s inbox and try to extract files from there.
One could setup a full mail server with a configuration or procmail to directly extract attachments into a directory.
I don’t really like any of these proposals because they are all more involved than setting up a SSH or FTP server. Also I don’t have experience with setting up and administrating mail servers.
Do you have suggestions or experiences to share?
The target system is Linux/Unix, but if you know something platform independent I’d like to hear, too.
The most suitable way is to set up an ESB with SMTP support, like ServiceMix or Mule. Mule is more straight-forward to get started with.
I am trying to understand how a solution will behave if deployed in a server farm. We have a Java web application which will talk to an FTP server for file uploads and downloads.
It is also desirable to protect the FTP server with a firewall, such that it will allow incoming traffic only from the web server.
AT the moment since we do not have a server farm, all requests to the FTP server come from the same IP (web server IP) making it possible to add a simple rule in the firewall. However, if the application is moved to a server farm, then I do not know which machine in the farm will make a request to the FTP server.
Just like the farm is hidden behind a facade for it's clients, is it hidden behind a facade for the services it might invoke, so that regardless of which machine from the farm makes the request to the FTP server, it always sees the same IP?
Are all server farms implemented the same way, or would this behavior depend on the type of server farm? I am thinking of using Amazon Elastic CLoud.
It depends very much on how your web cluster is configured. If your cluster is behind a NAT firewall, then yes, all outgoing connections will appear to come from the same address. Otherwise, the IP addresses will be different, but they'll almost certainly all be in a fairly small range of addresses, and you should be able to add that range to the firewall's exclude list, or even just list the IP address of each machine individually.
Usually you can enter cnames or subnets when setting up firewall rules, which would simplify the maintenance of them. You can also send all traffic through a load balancer or proxy. Thats essentially how any cloud/cluster/farm service works.
many client ips <-> load balancer <-> many servers
Recently we got a new server at the office purely for testing purposes. It is set up so that we can access it from any computer.
However today our ip got blocked from one of our other sites saying that our ip has been suspected of having a virus that sends spam emails. we learned this from the cbl http://cbl.abuseat.org/
So of course we turned the server off to stop this. The problem is the server must be on to continue developing our application and to access the database that is installed on it. Our normal admin is on vacation and is unreachable, and the rest of us are idiots(me included) in this area.
We believe that the best solution is to remove it from connecting to the internet but still access it on the lan. If that is a valid solution how would this be done or is there a better way? say blocking specified ports or whatever.
I assume that this server is behind a router? You should be able to block WAN connections to the server on the router and still leave it open to accepting LAN connection. Or you could restrict the IPs that can connect to the server to the development machines on the network.