Client /server model of network communication

can some some tell me what is meant by the client / server model of network communication?

See this networking tutorial
http://java.sun.com/docs/books/tutorial/networking/index.html
You could have asked both questions in the same post, as they are related.

Similar Messages

Client/server model and avoiding a registry lookup

Sorry if this question has been asked/answered before - I searched the forums and could not find the answer to my quesiton.
I am using RMI to model a fairly vanilla client/server protocol. Client to server communctions are no problem (yet :-)) . The problem is, that sometimes I want the server to initiate communcations to the client (I guess the client would be acting as the 'server' in those instances although the client is the one that makes the initial connection) Is there any way to do this without the server having to bind the client in the client's remote registry? That would require a open port and I want to avoid that for people who are behind firewalls. I was thinking the client could pass an instance of itself, or an instance of a bound stub, and as long as it implemented 'Remote' then it should be OK. I don't have a problem setting up a registry client side, but if I pass an instance of client that is either registry bound or unbound, as long as it implements Remote, (or rather an interface that extends Remote) will the server make remote calls on the client object?
Message was edited by:
SunDog

It's done all the time. What you're looking for is called "callback." Sun has a tutorial.
One note: Calling the client requires the client to open a port for communication. This happens when the client exports the remote object.

Client - Server over a network --- Where to begin?

I need to create a repository server-like applications on a network and have client access them. I have no idea where to start. I've looked at sockets, RMI, and SQL (I don't want to make a DB if I don't have to though), but I don't know if I'm even going in the right direction. Ideally the server would just be a collection of data to be accessed or modified and the clients would be GUIs designed to present and manipulate that data. I've done similar projects before, but never over a network, which is the part that is throwing me.
Any advice would be appreciated, as I have hit the wall.

I suggest you reconsider using a free DB like MySQL.
This is simple to setup and can be shared remotely by multiple clients and it persists the data you have.

How to construct a URL in client-server model

i wrote a prog, i use jdbc-odbc. URL="jdbc:odbc:filename",it runs very well while all on the SAME computer installed.
but if prog installed on a server and i work on a client-machine, it does'nt work with wrong message like: can not write to file because writesecurty and so on .
i guess i should give another url in form as: hostname + portnumber instead of the old one. is it true?
if yes, how can i get the portnumber of the server?
what else ground could it be?
has anybody experience with this topic, thanks a lot in advance

You must configure ODBC on the machine where the program is running to refer to the database on the remote system. Don't know how you would do that, it depends on the database and its ODBC driver. If possible, get a JDBC driver for your database and use it instead of JDBC-ODBC.

Client/server program validation - is it possible?

I've been mulling over this problem for a few days, and am starting to wonder if it's theoretically possible to find a solution. I'm not looking for specific code, this probably won't even be implemented in Java, I'm just wondering if there is a theoretical program model that would work in this situation.
The short version:
Validate the data generated by a client program, without knowing the original data.
The long version:
This is a "profiling" system for a MMOG (Massively Multiplayer Online Game). The MMOG is an internet based client/server graphical program where each client connects to the server and they interact with each other and the virtual world. They pay a monthly fee for access to the game. My program is not affiliated with the MMOG or its makers. I have no connections inside the company and cannot expect any cooperation from them.
The "profiling" system is also a client/server model. The client program runs in the background while the MMOG client is active. It accesses the memory of the MMOG client to retrieve information about the player's character. Then, possibly on request or maybe immediately, it sends the character data to our server.
What I want to validate is that the character data being sent is unmodified and actually comes from the MMOG program.
I can reasonably expect that with mild encryption and some sort of checksum or digest, the vast majority of problems can be avoided. However, I am not sure it's possible to completely secure the system.
I assume that the user has access to and knowledge of the profiler client and the MMOG client, their assembly code, and the ability to modify them or create new programs, leveraging that knowledge. I also assume that the user does not have access to or knowledge of either of the server applications - the MMOG server or mine.
In a worst-case scenario, there are several ways they could circumvent any security I have yet been able to think of. For instance, they could set up a fake MMOG client that had the data they wanted in memory, and let the profiler access that instead of the real thing. Or, they could rewrite the profiler to use the data they wanted and still encrypt it using whatever format I had specified.
I have been considering using some kind of buffer overflow vulnerability or remote execution technique that would allow me to run specific parts of the client program on command, or get information by request, something that could not be anticipated prior to execution and thus could not be faked. But this seems not only insecure for the client but also not quite solid enough, depending on how it was implemented.
Perhaps a series of apparently random validation codes, where the client does not know which one actually is doing the validation, so it must honor them all. Again, this is very conceptual and I'm sure that I'm not explaining them very well. I'm open to ideas.
If I don't come up with anything better, I would consider relying on human error and the fact that the user will not know, at first, the relevance of some of the data being passed between client and server. In this case, I would include some kind of "security handshake" that looks like garbage to the client but actually is validated on the server end. A modified program or data file would result in an invalid handshake, alerting the server (and me) that this client was a potential problem. The client would have no idea anything had gone wrong, because they would not know what data the server was expecting to receive.
I hope I have not confused anyone too much. I know I've confused myself....

Yes, that is the general model for all MMOGs these days - no data that can actually affect the game is safe if loaded from the client's computer. All character and world data is sent from server to client and stored in memory. Any information that is saved to the client's computer is for reference only and not used by the game engine to determine the results of actions/events etc.
My program accesses the MMOG client's memory while the game is running, and takes the character information from there. It does not have direct access to the MMOG server, and does not attempt to modify the data or the memory. Instead, it just encrypts it and sends it to our server, where the information is loaded into a database.
The security issue comes into play because our database is used for ranking purposes, and if someone were to hack my program, they could send invalid data to our servers and affect the rankings unfairly.
I'm just trying to think of a way to prevent that from happening.

Can i use forms 9i for client server applicaitons

Hi,
I have to build a client/server application.Right now, we are using oracle 9i and developer suite 10g. In one of the articles on OTN, it says that from forms 9i onwards, it's not supporting client/server model. Do i have to use 6i for this.
Thank you.
Sree.

The last Forms version that can be run in c/s mode is 6i.

Client server technology of oracl

Hi, I am sunil and beginner for oracle
I want to know some basic idea about client server technology

See this networking tutorial
http://java.sun.com/docs/books/tutorial/networking/index.html
You could have asked both questions in the same post, as they are related.

Network communication Xacute applets client - Mii server

Hi all,
I have a rather technical question.
Does anybody know what goes on from a network communication point of view when an applet on a irpt-page gets executed and fetches data from the Mii server?
Do these applets use RMI or some other method?
It's because we might have network issues, and I would like to know how the applets work on network level.
Our architecture is as follows:
On the client an irpt page is displayed in a browser (MSIE). The irpt page contains applets generated by Xacute queries. We also rely a lot on JS.
The client application communicates with the Mii server over the WAN.
So if someone can tell me which ports are used by the applets, would be great!
W.

Ok, on the server side indeed the applets connect to 5nn00. I love the debug option!
Now, on our WAN we have defined a QoS, for traffic prioritizing. So certain port numbers (or ip-adresses) get priority over the network. We added port 52000 (used by Mii) to this QoS, but unfortunately the traffic does not get prioritized.
The problem is that on the client side (Mii HTTP application), we cannot control which ports are opened (that's the OS).
On client side it could be port 4000 to 65999 or something. When we do port-prioritizing, this can never work.
So how do we configure our QoS? Prioritize everything going to and coming from the Mii server?
Anyone experience with that? I know it's not directly related to SAP and Mii, but when working with Mii one stumbles onto all kind of technologies
cheers!

Establish a connection through RF modem's on client & server side & to set up PPP communication for data transfer

hi
can any1 over here help me out in how to establish connection between 2 RF modem's for data transfer , between client & server USing LABVIEW?
I want to establish a connection between 2 PC's through RF modem on client & server side & to set up PPP communication for data transfer.
(I have tried data transfer through RS-232 using TCP/IP whn the 2 PC's are connected over ethernet... which is working.
I also tried connecting loopback cable between 2 PC's COM port & geting data transfer using VIsa configure serial port & other visa functions ... which is working)
can u guide me how to establish connection between 2 RF modem's using LABview?
& how does the data transfer take place between 2 RF modems through RS-232?
is it using TCP/IP?
If you got any links to go abt this issue do send me related links .. or any examples .....
I am currently using Labview version 8.
Waiting in anticipation.. reply ASAP..
thanking you
Regards
Yogan..

Howdy yogan,
Maybe you could clarify a few things for me, and we'll see how we can help ya. TCP/IP protocol occurs through an ethernet connection; RS-232 communication occurs through an RS-232 serial connection, typically through a cable that has a DB9 connector on both ends. Do you mean that the RF modems in question have the option to communicate via RS-232 and/or via TCP/IP ethernet? Specific information like the manufacturer of your RF modems, the model number of your RF modems, and how you connect the modems to the PC would enable us to give you more efficient support.
You can check our Instrument Driver Network (IDNet) to see if a plug-and-play/IVI driver already exists for your RF modem. (You'll need to know its manufacturer and model number.) In the case that you do find an IDNet driver for your modem, you can use this KnowledgeBase article for instructions on how to use the driver.
Another excellent resource to consider is the NI Example Finder. You can access this within LabVIEW by navigating to Help»Find Examples and then searching for serial or TCP/IP examples.
Message Edited by pBerg on 03-10-2008 04:35 PM
Warm regards,
pBerg

The remote server returned an error: (401) Unauthorized. while running client context using sharepoint client object model

Hi,
I have started using the client object model so that i do not have to go to sharepoint admins to perform some basic operations on remote server. While assigning list item level permission i am getting following error, could you please help. thanks.
The remote server returned an error: (401) Unauthorized.
   at
System.Net.HttpWebRequest.GetResponse()
   at
Microsoft.SharePoint.Client.SPWebRequestExecutor.Execute()
   at
Microsoft.SharePoint.Client.ClientContext.EnsureFormDigest()
   at
Microsoft.SharePoint.Client.ClientContext.ExecuteQuery()
   at
SetDowntimeItemPermission.SetPermission.Main(String[] args) in

it seems your request was unauthenticated i'm not sure are you using a web application with FBA or desktop application my suggestion would be try to impersonate your request by passing network credentials (COM works on network credentials )
NetworkCredential credentials = new NetworkCredential("username", "pwd", "domain");
ClientContext context = new ClientContext("http://site-url");
context.Credentials = credentials;
Best Regards, Ashutosh | SharePoint World

Need help clarifying client/server TNS communication

Im trying to get a clearer understanding of service/listener registration in the Oracle client/server architechure. Feel free to point out errors in my understanding.
When an Oracle client connects to the server, it forms its connect descriptor based on the clients tnsnames.ora file. The client then checks the specified port on the host in the connect descriptor for a listener that is registered with the service defined in the
(CONNECT_DATA =
(SERVICE_NAME = TESTSERVICE)
portion of the client's tnsnames file. Correct?
Does the listener gets its list of SIDs its registered with from the SID_LIST section of the listener.ora file or the tnsnames file?
If the listener gets its list of SIDs to register with from the tnsnames file, is that the tnsnames file on the server?
If so, then what is the SID_LIST used for in the listener.ora file?
Im trying to connect the dots and any help would be much appreciated.
Thanks,

Reading below documents would help you understand how client/server TNS communication works:-
Listener Architecture
http://download-east.oracle.com/docs/cd/B14117_01/network.101/b10775/architecture.htm#sthref445
Configuring Naming Methods
http://download-east.oracle.com/docs/cd/B14117_01/network.101/b10775/naming.htm
Configuring and Administering the Listener
http://download-east.oracle.com/docs/cd/B14117_01/network.101/b10775/listenercfg.htm

About the communication issues in the client-server program

About the communication issues in the client-server program
Hi, I have some questions about the communication issues in a java project, which is basically the client and server architecture. In brief, the client, written in java, can be deployed anywhere, and in the following part, assume it is in the LAN (Local Area Network) which is connnected to the internet through the firewall and/or proxy, and the server, written in
java too, simply provides the listening service on a port in a remote machine. And assume the server is connected to the internet directly so that the scenario can be simple to focus on the core questions.
My questions are as follows:
1 About the relationship between the communication port and protocol
Generally, protocols at the application level like HTTP, FTP have their own default port, e.g., HTTP is corresponding to 80,
FTP is to 25. But it is NOT necessary for the web server to provide the HTTP listening service at port 80, right? E.g, Tomcat provides the HTTP listening service at 8080. So it means the default relationship between the application protocl and their port is some routine, which is not necessary to follow, right?
2 Assume a LAN connected to the internet through a proxy, which only allows HTTP protocol, then questions are:
2.1 Does the proxy recognize the HTTP request from the client by the port number (carried in the request string)? For example, when the server provides the HTTP listening service at 80, then the request from the client will include the port number 80, then the proxy will parse such info and decide if or not the request can be out.
2.2 Does the proxy recognize the HTTP request from the client by protocol (carried in the request string)? For example, the protocol used in the communicatin should be included in the request, then the proxy can parse it to make the decision.
3 In java programm, if using the HTTP protcol, then on the client: the corresponding API is java.net.URLConnection, right?
If using the TCP protocol directly, then on the client:the corresponding API is java.net.Socket, right? In both cases, the server side use the same API, java.net.ServerSocket?
Is it correct to say that the communication by Socket is faster than URLConnection?
4 Take MSN messenger for example, which protocol does it use? Since proxy configure is only the possible option, so I guess generally the TCP protocol is used directly so that the better perfomrance can be achieved, right?
5 Given 3 computers within the same LAN, can the client, proxy, server environment above be correctly simulated? If so, can
you recommend me some typical proxy program so that I can install it to configure such an enviroment to perform some test?
6 I guess there should be some software to find out which port number a given program/process is going through to connect to
the remote machine, and which port number a given program/process is listening on? Also, what protocl is used in the given
communication.
7 Finally, regarding each of the above questions, it will be highly appreciated that if you can recommed some references,
tutorials, books etc. In summary, what I care about is how to enable the java client behind the proxy and firewall to
communicate with the remote server without problems, so if you know some good tutorials plz let me know and thx in advance!
Finally, thanks for your attention so such long questions =).

FTP is to 25. But it is NOT necessary for the web
server to provide the HTTP listening service at port
80, right? E.g, Tomcat provides the HTTP listening
service at 8080. So it means the default relationship
between the application protocl and their port is
some routine, which is not necessary to follow,
right?Not sure what you're saying here.
There must be a server listening on some port. The client must know what port that is. If you open the connection using the Socket class, you'll explicitly specify the port. If you use some higher level class like URLConnection or something in the commons Net package, there's probably a default port that will be used if you don't explicitly specify another.
There's no way for the client to know that the HTTP request will go to port 80 instead of port 8080. If you think the the client contacts the server without explicitly naming a port, and then asks the server "get me your HTTP server", and the port is determined from that, you're mistaken.
Not sure if you're thinking that, but it sounded like you might be.
2 Assume a LAN connected to the internet through
a proxy, which only allows HTTP protocol, then
questions are:
2.1 Does the proxy recognize the HTTP request
from the client by the port number (carried in the
request string)? For example, when the server
provides the HTTP listening service at 80, then the
request from the client will include the port number
80, then the proxy will parse such info and decide if
or not the request can be out. I'm not sure, but I think most proxies and firewalls are configured by ports. I thought I'd heard of more sophisticated, higher-level ones that could understand the content to some degree, but I don't know anything about those.
3 In java programm, if using the HTTP protcol,
then on the client: the corresponding API is
java.net.URLConnection, right?That's one way.
You might want to look into this:
http://jakarta.apache.org/commons/httpclient/
If using the TCP protocol directly, then on the
client:the corresponding API is java.net.Socket,
right? In both cases, the server side use the same
API, java.net.ServerSocket? A Java client will user Socket, and a Java server will use ServerSocket and Socket.
Is it correct to say that the communication by Socket
is faster than URLConnection?Probably not.

How to set a default firefox homepage on client workstations on a network with a server running windows 2003 server?

I am running a small client server network with about 27 client machines and windows server 2003 is the server OS. I want the default webpage on firefox to display our department homepage when users log on. I have set IE7 already in the groups policy in the ISS section but this only affects IE7. Any idea how I can do this with Firefox?

You can set or lock default prefs via a mozilla.cfg file.
Pref: browser.startup.homepage , see http://kb.mozillazine.org/browser.startup.homepage
defaultPref(); // set new default value
pref(); // set pref, but allow changes
lockPref(); // lock pref, disallow changes
See http://kb.mozillazine.org/Locking_preferences

Can we write client object model code with Server object model?

Hi everyone,
I have to create one timer job using client object model (C#) in Sharepoint 2010 template on feature activation. Is it possible to write the code of client object in sharepoint empty project to create timer job? If yes/no? then why?
Thanks in advance!!!

Hi ShindeK,
Yes you can used CSOM in Sharepoint but Timer jobs run directly on the server. The Client Side Object Model is a wrapper that brokers its calls to the server via the built in web services that SharePoint provides.
You will not get any performance gains in this scenario using CSOM. You should use the full server object model of SharePoint
SharePoint 2010 also has three Client Object Models (Managed, Silverlight, JavaScript) which are meant to be used by code accessing SharePoint remotely.
--You can also used powershell script in timer job
Chekc the link which cann help you step by step CSOM in Sharepoint timer job
http://www.youtube.com/watch?v=Z7wHj-bSk0g
You can also try the below link....
https://bramdejager.wordpress.com/2013/08/02/using-csom-and-powershell-to-query-sharepoint-online-or-on-premise/
http://stackoverflow.com/questions/3656920/run-sharepoint-timer-jobs-from-powershell
Please mark the Answer and Vote me if you think that it will help you to resolved your issue

What is best way to secure client/server communication?

Hi all, I have a question for you. What is the best method for ensuring a secure communication through a client/server stream socket implementation?
I currently have a server that talks to several clients for various tasks. I would like to make all communication between the server and clients secure. In other words when one of my clients accepts an incoming connection I would like to verify that the server is really who they are talking with, and also that the data that is being received is indeed not tampered with.
Is SSL the correct technology to use with this? And if so, what is the general outline of steps I need to follow to get an SSL connection? I mean do I need certificates and all that stuff?
Thanks in advance for any help you may be able to provide.

The more I look into SSL the more it appears it is only for web servers. My app is not web server based. Is SSL not the correct way to go on this then?

Client /server model of network communication

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