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• Theoretical minimum round-trip-time for a packet to travel over/under the North Atlantic Sea?

  - by knorv

  I'm doing some performance tuning and capacity planning for a low-latency application and have the following question: What is the theoretical minimum round-trip time for a packet sent between a host in London and one in New York?

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• Communication with different social networks, strategy pattern?

  - by bclaessens

  Hi For the last few days I've been thinking how I can solve the following programming problem and find the ideal, flexible programming structure. (note: I'm using Flash as my platform technology but that shouldn't matter since I'm just looking for the ideal design pattern). Our Flash website has multiple situations in which it has to communicate with different social networks (Facebook, Netlog and Skyrock). Now, the communication strategy doesn't have to change multiple times over one "run". The strategy should be picked once (at launch time) for that session. The real problem is the way the communication works between each social network and our website. Some networks force us to ask for a token, others force us to use a webservice, yet another forces us to set up its communication through javascript. The problem becomes more complicated when our website has to run in each network's canvas. Which results in even more (different) ways of communicating. To sum up, our website has to work in the following cases: standalone on the campaign website url (user chooses their favourite network) communicate with netlog OR communicate with facebook OR communicate with skyrock run in a netlog canvas and log in automatically (website checks for netlog parameters) run in a facebook canvas and log in automatically (website checks for facebook params) run in a skyrock canvas and log in automatically (website checks for skyrock params) As you can see, our website needs 6 different ways to communicate with a social network. To be honest, the actual significant difference between all communication strategies is the way they have to connect to their individual network (as stated above in my example). Posting an image, make a comment, ... is the same whether it runs standalone or in the canvas url. WARNING: posting an image, posting a comment DOES differ from network to network. Should I use the strategy pattern and make 6 different communication strategies or is there a better way? An example would be great but isn't required ;) Thanks in advance

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• Social Network directed Graph Library? .NET

  - by MRFerocius

  Hello everybody, I am on a project where I have multiple users of a portal and they are connected to other users of the portal, now we are asked to draw a "Social Network" relationship graph to see the relationships. The constraint is that this graph has to be seen on the WEB BROWSER. The graph has to be something like: Is there any C# library or component to draw this type of graphs? We have already checked these: http://flare.prefuse.org/ http://www.yworks.com/en/products_yfiles_practicalinfo_gallery.html .NET graph library around? http://quickgraph.codeplex.com/ https://graphsharp.codeplex.com/ http://research.microsoft.com/en-us/downloads/f1303e46-965f-401a-87c3-34e1331d32c5/default.aspx http://sourceforge.net/projects/zedgraph/ But I want to check if you already used some other and your feedback... Thanks in advanced!

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• Remote Computer Monitoring in Java....

  - by vs4vijay

  I have Assigned a Project on "Remote Computer Monitoring "...(To access Other PC like VNC) and i decided to do this in Java(Because of Platform Independency..)... and my java classes are goin on and we are at Threading.. so tell me where to start the project ???... What Should i Learn More...?? and is there any prebuild interfaces for this???... PS: i have to Access the Remote Machine Graphically Like TeamViewer and Do some filetransfer Stuff....

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• problem with kCFSocketReadCallBack

  - by zp26

  Hello. I have a problem with my program. I created a socket with "kCFSocketReadCallBack. My intention was to call the "acceptCallback" only when it receives a string to the socket. Instead my program does not just accept the connection always goes into "startReceive" stop doing so and sometimes crash the program. Can anybody help? Thanks readSocket = CFSocketCreateWithNative( NULL, fd, kCFSocketReadCallBack, AcceptCallback, &context ); static void AcceptCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) // Called by CFSocket when someone connects to our listening socket. // This implementation just bounces the request up to Objective-C. { ServerVistaController * obj; #pragma unused(address) // assert(address == NULL); assert(data != NULL); obj = (ServerVistaController *) info; assert(obj != nil); #pragma unused(s) assert(s == obj->listeningSocket); if (type & kCFSocketAcceptCallBack){ [obj acceptConnection:*(int *)data]; } if (type & kCFSocketAcceptCallBack){ [obj startReceive:*(int *)data]; } } -(void)startReceive:(int)fd { CFReadStreamRef readStream = NULL; CFIndex bytes; UInt8 buffer[MAXLENGTH]; CFStreamCreatePairWithSocket( kCFAllocatorDefault, fd, &readStream, NULL); if(!readStream){ close(fd); [self updateLabel:@"No readStream"]; } CFReadStreamOpen(readStream); [self updateLabel:@"OpenStream"]; bytes = CFReadStreamRead( readStream, buffer, sizeof(buffer)); if (bytes < 0) { [self updateLabel:(NSString*)buffer]; close(fd); } CFReadStreamClose(readStream); }

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• Why sockets does not die when server dies? Why socket dies when server is alive?

  - by Roman

  I try to play with sockets a bit. For that I wrote very simple "client" and "server" applications. Client: import java.net.*; public class client { public static void main(String[] args) throws Exception { InetAddress localhost = InetAddress.getLocalHost(); System.out.println("before"); Socket clientSideSocket = null; try { clientSideSocket = new Socket(localhost,12345,localhost,54321); } catch (ConnectException e) { System.out.println("Connection Refused"); } System.out.println("after"); if (clientSideSocket != null) { clientSideSocket.close(); } } } Server: import java.net.*; public class server { public static void main(String[] args) throws Exception { ServerSocket listener = new ServerSocket(12345); while (true) { Socket serverSideSocket = listener.accept(); System.out.println("A client-request is accepted."); } } } And I found a behavior that I cannot explain: I start a server, than I start a client. Connection is successfully established (client stops running and server is running). Then I close the server and start it again in a second. After that I start a client and it writes "Connection Refused". It seems to me that the server "remember" the old connection and does not want to open the second connection twice. But I do not understand how it is possible. Because I killed the previous server and started a new one! I do not start the server immediately after the previous one was killed (I wait like 20 seconds). In this case the server "forget" the socket from the previous server and accepts the request from the client. I start the server and then I start the client. Connection is established (server writes: "A client-request is accepted"). Then I wait a minute and start the client again. And server (which was running the whole time) accept the request again! Why? The server should not accept the request from the same client-IP and client-port but it does!

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• need for tcp fine-tuning on heavily used proxy server

  - by Vijay Gharge

  Hi all, I am using squid like Internet proxy server on RHEL 4 update 6 & 8 with quite heavy load i.e. 8k established connections during peak hour. Without depending much on application provider's expertise I want to achieve maximum o/p from linux. W.r.t. that I have certain questions as following: How to find out if there is scope for further tcp fine-tuning (without exhausting available resources) as the benchmark values given by vendor looks poor! Is there any parameter value that is available from OS / network stack that will show me the results. If at all there is scope, how shall I identify & configure OS tcp stack parameters i.e. using sysctl or any specific parameter Post tuning how shall I clearly measure performance enhancement / degradation ?

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• Neural Network Basics

  - by Stat Onetwothree

  I'm a computer science student and for this years project, I need to create and apply a Genetic Algorithm to something. I think Neural Networks would be a good thing to apply it to, but I'm having trouble understanding them. I fully understand the concepts but none of the websites out there really explain the following which is blocking my understanding: How the decision is made for how many nodes there are. What the nodes actually represent and do. What part the weights and bias actually play in classification. Could someone please shed some light on this for me? Also, I'd really appreciate it if you have any similar ideas for what I could apply a GA to. Thanks very much! :)

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• Command or tool to display list of connections to a Windows file share

  - by BizTalkMama

  Is there a Windows command or tool that can tell me what users or computers are connected to a Windows fileshare? Here's why I'm looking for this: I've run into issues in the past where our deployment team has deployed BizTalk applications to one of our environments using the wrong bindings, leaving us with two receive locations pointing to the same file share (i.e. both dev and test servers point to dev receive location uri). When this occurs, the two environments in question tend to take turns processing the files received (meaning if I am attempting to debug something in one environment and the other environment has picked the file up, it looks as if my test file has disappeared into thin air). We have several different environments, plus individual developer machines, and I'd rather not have to check each individually to find the culprit. I'm looking for a quick way to detect what locations are connected to the share once I notice my test files vanishing. If I can determine the connections that are invalid, I can go directly to the person responsible for that environment and avoid the time it takes to randomly ask around. Or if the connections appear to be correct, I can go directly to troubleshooting where in the process the message gets lost. Any suggestions?

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• Security review of an authenticated Diffie Hellman variant

  - by mtraut

  EDIT I'm still hoping for some advice on this, i tried to clarify my intentions... When i came upon device pairing in my mobile communication framework i studied a lot of papers on this topic and and also got some input from previous questions here. But, i didn't find a ready to implement protocol solution - so i invented a derivate and as i'm no crypto geek i'm not sure about the security caveats of the final solution: The main questions are Is SHA256 sufficient as a commit function? Is the addition of the shared secret as an authentication info in the commit string safe? What is the overall security of the 1024 bit group DH I assume at most 2^-24 bit probability of succesful MITM attack (because of 24 bit challenge). Is this plausible? What may be the most promising attack (besides ripping the device out off my numb, cold hands) This is the algorithm sketch For first time pairing, a solution proposed in "Key agreement in peer-to-peer wireless networks" (DH-SC) is implemented. I based it on a commitment derived from: A fix "UUID" for the communicating entity/role (128 bit, sent at protocol start, before commitment) The public DH key (192 bit private key, based on the 1024 bit Oakley group) A 24 bit random challenge Commit is computed using SHA256 c = sha256( UUID || DH pub || Chall) Both parties exchange this commitment, open and transfer the plain content of the above values. The 24 bit random is displayed to the user for manual authentication DH session key (128 bytes, see above) is computed When the user opts for persistent pairing, the session key is stored with the remote UUID as a shared secret Next time devices connect, commit is computed by additionally hashing the previous DH session key before the random challenge. For sure it is not transfered when opening. c = sha256( UUID || DH pub || DH sess || Chall) Now the user is not bothered authenticating when the local party can derive the same commitment using his own, stored previous DH session key. After succesful connection the new DH session key becomes the new shared secret. As this does not exactly fit the protocols i found so far (and as such their security proofs), i'd be very interested to get an opinion from some more crypto enabled guys here. BTW. i did read about the "EKE" protocol, but i'm not sure what the extra security level is.

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• How to get the system HTTP proxy configuration in Java

  - by Auron

  Is it possible to get the system proxy configuration in Java? In the Java Control Panel, you can set a proxy configuration. How can I access to that proxy configuration in order to open URL connections behind a proxy?

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• SslStream.ReadByte() blocks thread?

  - by alex

  I'm trying to write an Imap4 client. For that I use a SslStream to Connect to the Server. Everything's fine until I send the "Login" command. When I try to get an Answer to it, SslStream.ReadByte() block the thread. The result is that my programm crashes always. Whats happening here?? Code: if (ssl) { s = stream; } int cc = 0; MessageBox.Show("entered"); while (true) { int xs = s.ReadByte(); MessageBox.Show(xs.ToString()); if (xs > 0) { buf.Add((byte)xs); cc++; if (xs == '\n') { break; } if (cc > 10) MessageBox.Show(en.GetString(buf.ToArray())); } else { break; } } MessageBox.Show("left");

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• What to do when ServerSocket throws IOException

  - by s5804

  Basically I want to create a rock solid server. while (keepRunning.get()) { try { Socket clientSocket = serverSocket.accept(); ... spawn a new thread to handle the client ... } catch (IOException e) { e.printStackTrace(); // NOW WHAT? } } In the IOException block, what to do? Is the Server socket at fault so it need to be recreated? For example wait a few seconds and then serverSocket = ServerSocketFactory.getDefault().createServerSocket(MY_PORT); However if the server socket is still OK, then it is a pity to close it and kill all previously accepted connections that are still communicating.

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• Depmod - unresolved symbols in rt73 module

  - by Xolstice

  I'm trying to install a linux driver for my wireless network card (D-Link DWL-G510) on my Red Hat Linux 7.1 machine with a 2.4.37.9 kernel. I downloaded the serial monkey driver from the sourceforge site and was able to successfully compile the module. However, whenever I do a "make install", the make script executes a "depmod -a" command which then complains with the message: "Unresolved symbols in /lib/modules/2.4.37.9/extra/rt73.o". I then executed a "depmod -e" command to show unresolved symbols and it indicates the following information: request_firmware_Rsmp_38ce5074 release_firmware_Rsmp_33934162 I did a grep on the above information and it showed no source files making reference to it. I searched for it on google and it returned no results. Can anyone help?

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• What happens when we say "listen to a port" ?

  - by smwikipedia

  Hi, When we start a server application, we always need to speicify the port number it listens to. But how is this "listening mechanism" implemented under the hood? My current imagination is like this: The operating system associate the port number with some buffer. The server application's responsibiligy is to monitor this buffer. If there's no data in this buffer, the server application's listen operation will just block the application. When some data arrives from the wire, the operating system will know that check the data and see if it is targed at this port number. And then it will fill the buffer. And then OS will notify the blocked server application and the server application will get the data and continue to run. Question is: If the above scenario is correct, how could the opearting system know there's data arriving from wire? It cannot be a busy pooling. Is it some kind of interrupt-based mechanism? If there's too much data arriving and the buffer is not big enough, will there be data loss? Is the "listen to a port" operation really a blocking operation? Many thanks.

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• How do I find the IP address of a GPRS modem?

  - by Hanno Fietz

  I want to pull data from a device that is accessed via a serial protocol and has a GPRS modem attached which should allow transparent access over an IP connection. It seems to me that this approach is upside down, because how should I know at which IP address the device currently is? Unfortunately, the device itself is rather dumb, so I can't make it send something to my server, which would reveal the current IP. For home routers on dialup lines, there's dynamic DNS services. Is there something equivalent in the mobile world? Each modem would, of course, have its phone number as a reliable address, but how does that help me? Practically all material on GPRS etc. that I can find online seems to be concerned with initiating the connection from the modem side, since that's what the system is designed for.

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• How to access a web service behind a NAT?

  - by jr

  We have a product we are deploying to some small businesses. It is basically a RESTful API over SSL using Tomcat. This is installed on the server in the small business and is accessed via an iPhone or other device portable device. So, the devices connecting to the server could come from any number of IP addresses. The problem comes with the installation. When we install this service, it seems to always become a problem when doing port forwarding so the outside world can gain access to tomcat. It seems most time the owner doesn't know router password, etc, etc. I am trying to research other ways we can accomplish this. I've come up with the following and would like to hear other thoughts on the topic. Setup a SSH tunnel from each client office to a central server. Basically the remote devices would connect to that central server on a port and that traffic would be tunneled back to Tomcat in the office. Seems kind of redundant to have SSH and then SSL, but really no other way to accomplish it since end-to-end I need SSL (from device to office). Not sure of performance implications here, but I know it would work. Would need to monitor the tunnel and bring it back up if it goes done, would need to handle SSH key exchanges, etc. Setup uPNP to try and configure the hole for me. Would likely work most of the time, but uPNP isn't guaranteed to be turned on. May be a good next step. Come up with some type of NAT transversal scheme. I'm just not familiar with these and uncertain of how they exactly work. We have access to a centralized server which is required for the authentication if that makes it any easier. What else should I be looking at to get this accomplished?

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• Network message serialization for game

  - by George R

  Exit-games make a network library product called photon, and they have and actively develop a limited mmo demo. Rather than shooting off json or XML, etc. saying "MovePlayer" (with associated params), they nut that message down to a 2 digit int, via an enum - something like Operations.MovePlayer. There's no denying that a 2 digit int is smaller than a longer string, however I really hate the idea of statically burning each and every message into an enum. Would there be an alternative way to have a MessageID property assign itself a unique 2 digit int based on a lookup table or something? Has anyone dealt with this kind of thing before?

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• Ping broadcast on Win XP SP3

  - by PaulH

  I'm trying to ping the broadcast address 255.255.255.255 on WinXP SP3. If I use the command line, I get host error: C:\>ping 255.255.255.255 Ping request could not find host 255.255.255.255. Please check the name and try again. If I try a C++ program using the iphlpapi, IcmpSendEcho() fails and GetLastError returns 11010 IP_REQ_TIMED_OUT. HANDLE h = ::IcmpCreateFile(); IPAddr broadcast = inet_addr( "255.255.255.255" ); BYTE payload[ 32 ] = { 0 }; IP_OPTION_INFORMATION option = { 255, 0, 0, 0, 0 }; // a buffer with room for 32 replies each containing the full payload std::vector< BYTE > replies( 32 * ( sizeof( ICMP_ECHO_REPLY ) + 32 ) ); DWORD res = ::IcmpSendEcho( h, broadcast, payload, sizeof( payload ), &option, &replies[ 0 ], replies.size(), 1000 ); ::IcmpCloseHandle( h ); I can ping the local broadcast 192.168.0.255 with no problem. What do I need to do to ping the global broadcast? Thanks, PaulH

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• Paramiko ssh output stops at --more--

  - by Anesh

  The output stops printing at --more-- any idea how to get the end of the output >>> import paramiko >>> ssh = paramiko.SSHClient() >>> ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy()) >>> conn=ssh.connect("ipaddress",username="user", password="pass") >>> channel = ssh.invoke_shell() >>> channel.send("en\n") 3 >>> channel.send("password\n") 9 >>> channel.send("show security local-user-list\n") 30 >>> results = '' >>> channel.send("\n") 1 >>> results += channel.recv(5000) >>> print results bluecoat>en Password: bluecoat#show security local-user-list Default List: local_user_database Append users loaded from file to default list: false local_user_database Lockout parameters: Max failed attempts: 60 Lockout duration: 3600 Reset interval: 7200 Users: Groups: admin_local Lockout parameters: Max failed attempts: 60 Lockout duration: 3600 Reset interval: 7200 Users: <username> Hashed Password: Enabled: true Groups: <username> Hashed Password: Enabled: true **--More--** As you can see above the output stops printing at --more-- any idea how to get the output to print till the end.

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• How do I get current network location name?

  - by Devara Gudda

  In system network preference there are some location names.How to get the current or active network location name and list of all network locations? I guess SystemConfiguration.framework supports this but i didn't get exactly which API to use.Thanks in advance for your answer. RegardsDevara Gudda

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• Python - network buffer handling question...

  - by Patrick Moriarty

  Hi, I want to design a game server in python. The game will mostly just be passing small packets filled with ints, strings, and bytes stuffed into one message. As I'm using a different language to write the game, a normal packet would be sent like so: Writebyte(buffer, 5); // Delimit type of message Writestring(buffer, "Hello"); Sendmessage(buffer, socket); As you can see, it writes the bytes to the buffer, and sends the buffer. Is there any way to read something like this in python? I am aware of the struct module, and I've used it to pack things, but I've never used it to actually read something with mixed types stuck into one message. Thanks for the help.

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• How to transfer large files from desktop to server ( .NET)

  - by rahulchandran

  I am writing a .NET 2.0 based desktop client that will send large files ( well largish under 2GB) to a server. Need to develop the server as well. Server can be on any technology It should be secure so an underlying SSL stream is needed What are my options. Any obvious caveats etc I should be aware of To my mind the simplest solution is to open a tcp\ip connection over SSL to the server and send n packets each of size M bytes and then have the server append the chunks to the file and finally send an EOF packet as well IS this horrible. Will the perf suck on the server with all these disk writes What are any other clever options. I am limited to .NET 2.0 on the client if I did move to a WCF client will it buy be something magical and cool for this scenario Thanks

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• Which cms or script for social network wiki?

  - by Jason

  Hi, I am building a social network. I need a cms that will allow users to contribute content. Each content item will need to have a google map, list of features, ratings, comments, etc. And the content must be editable by other users with revision control. Also, each user should have a profile with their bookmarked content items, contributed items, comments, etc. It's very important that I can create a template for the wiki/content entries so that each item looks uniform. (and as a kick in the teeth, I would like to be able to search for wiki items using a radial search or map) Joomla was my first choice, as I've used it for many projects, but the wiki functionality is not there. I was also setting up a grou.ps site, but the wiki is so-so - not feature rich and it really doesn't have the option I need. Additionally, I know someone out there will mention Drupal. I may consider it if I can see it put to use without and overabundance of custom programming (I don't mind initial coding, but drupal requires constant coding & recoding - with this site, I dont' have that time commitment) I thought about using mediawiki with buddypress, but i'm not sure if that's the way to go. Thoughts?

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• Get local network interface addresses using only proc?

  - by Matt Joiner

  How can I obtain the (IPv4) addresses for all network interfaces using only proc? After some extensive investigation I've discovered the following: ifconfig makes use of SIOCGIFADDR, which requires open sockets and advance knowledge of all the interface names. It also isn't documented in any manual pages on Linux. proc contains /proc/net/dev, but this is a list of interface statistics. proc contains /proc/net/if_inet6, which is exactly what I need but for IPv6. Generally interfaces are easy to find in proc, but actual addresses are very rarely used except where explicitly part of some connection. There's a system call called getifaddrs, which is very much a "magical" function you'd expect to see in Windows. It's also implemented on BSD. However it's not very text-oriented, which makes it difficult to use from non-C languages.

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