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  • Apache HttpClient CoreConnectionPNames.CONNECTION_TIMEOUT does nothing ?

    - by Maxim Veksler
    Hi, I'm testing some result from HttpClient that looks irrational. It seems that setting CoreConnectionPNames.CONNECTION_TIMEOUT = 1 has no effect because send request to different host return successfully with connect timeout 1 which IMHO can't be the case (1ms to setup TCP handshake???) Am I misunderstood something or is something very strange going on here? The httpclient version I'm using as can be seen in this pom.xml is <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.0.1</version> <type>jar</type> </dependency> Here is the code: import java.io.IOException; import java.util.Random; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.ClientProtocolException; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.client.methods.HttpUriRequest; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.params.CoreConnectionPNames; import org.apache.http.util.EntityUtils; import org.apache.log4j.Logger; public class TestNodeAliveness { private static Logger log = Logger.getLogger(TestNodeAliveness.class); public static boolean nodeBIT(String elasticIP) throws ClientProtocolException, IOException { try { HttpClient client = new DefaultHttpClient(); // The time it takes to open TCP connection. client.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 1); // Timeout when server does not send data. client.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 5000); // Some tuning that is not required for bit tests. client.getParams().setParameter(CoreConnectionPNames.STALE_CONNECTION_CHECK, false); client.getParams().setParameter(CoreConnectionPNames.TCP_NODELAY, true); HttpUriRequest request = new HttpGet("http://" + elasticIP); HttpResponse response = client.execute(request); HttpEntity entity = response.getEntity(); if(entity == null) { return false; } else { System.out.println(EntityUtils.toString(entity)); } // Close just in case. request.abort(); } catch (Throwable e) { log.warn("BIT Test failed for " + elasticIP); e.printStackTrace(); return false; } return true; } public static void main(String[] args) throws ClientProtocolException, IOException { nodeBIT("google.com?cant_cache_this=" + (new Random()).nextInt()); } } Thank you.

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  • Plain-English tutorial on artificial neural networks?

    - by Stuart
    I've Googled, StackOverflowed, everything, and I cannot seem to find a tutorial I can understand. I understand the concept of genetic algorithms, and how to implement them, (Though I haven't tried) but I cannot grasp the concept of neural networks. I know vaguely how they work... And that's about it. Could someone direct me to a tutorial that could help someone who has not even graduated middle school yet? Sure, I'm several years ahead of the majority of people my grade, but I don't understand summation, (which I apparently need if I don't want a simple binary output) vectors, and other things that I apparently should know. Is there a simple, bare-bones tutorial for neural networks? After I learn the basics, I'll proceed to more difficult ones. Preferably, they would be in Java. Thanks!

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  • Inform me when site (server) is online again

    - by dede
    When I ping one site it returns "Request timed out". I want to make little program that will inform me (sound beep or something like that) when this server is online again. No matter in which language. I think it should be very simple script with a several lines of code. So how to write it?

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  • Monitor network connectivity in WP7 apps

    - by Daniel Moth
    Most interesting Windows Phone apps rely on some network service for their functionality. So at some point in your app you may need to know programmatically if there is network connection available or not. For example, the Translator by Moth app relies on the Bing Translation service for translations. When a request for translation (text or voice) is made, the network call may fail. The failure reason is not evident from any of the return results, so I check the connection to see if it is present. Dependent on that, a different message is shown to the user. Before the translation phase is even reached, at the app start up time the Bing service is queried for its list of  languages; in that case I don't want to show the user a message and instead want to be notified when the network is available in order to send the query out again. So for those two requirements (which I imagine are common in other apps) I wrote a simple wrapper MyNetwork static class to the framework APIs: Call once MyNetwork.MonitorNetworkAvailability() method so it monitors the network change At any time check the MyNetwork.IsConnected property to check for network presence Subscribe to its MyNetwork.ConnectionEstablished event Optionally, during debugging use its MyNetwork.ChangeStatus method to simulate a change in network status As usual, there may be better ways to achieve this, but this class works perfectly for my scenarios. You can download the code here: MyNetworks.cs. Comments about this post welcome at the original blog.

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  • Artifical neural networks height-weight problem

    - by hammid1981
    i plan to use neurodotnet for my phd thesis, but before that i just want to build some small solutions to get used to the dll structure. the first problem that i want to model using backward propagation is height-weight ratio. I have some height and weight data, i want to train my NN so that if i put in some weight then i should get correct height as a output. i have 1 input 1 hidden and 1 output layer. Now here is first of many things i cant get around :) 1. my height data is in form of 1.422, 1.5422 ... etc and the corresponding weight data is 90 95, but the NN takes the input as 0/1 or -1/1 and given the output in the same range. how to address this problem

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  • whats the diference between train, validation and test set, in neural networks?

    - by Daniel
    Im using this library http://pastebin.com/raw.php?i=aMtVv4RZ to implement a learning agent. I have generated the train cases, but i dont know for sure what are the validation and test sets, the teacher says: 70% should be train cases, 10% will be test cases and the rest 20% should be validation cases. Thanks. edit i have this code, for training.. but i have no ideia when to stop training.. def train(self, train, validation, N=0.3, M=0.1): # N: learning rate # M: momentum factor accuracy = list() while(True): error = 0.0 for p in train: input, target = p self.update(input) error = error + self.backPropagate(target, N, M) print "validation" total = 0 for p in validation: input, target = p output = self.update(input) total += sum([abs(target - output) for target, output in zip(target, output)]) #calculates sum of absolute diference between target and output accuracy.append(total) print min(accuracy) print sum(accuracy[-5:])/5 #if i % 100 == 0: print 'error %-14f' % error if ? < ?: break

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  • Search network device from LAN through my C++ application and change the IP address

    - by Arun Kumar K S
    I am developing an application in C++ to communicate with my network device. I used UDP classes to search the device from the network. I done the code in such a way that from my application a broadcast message will send to the local network. The device will respond to the broadcast message and the application will get the IP address from that response. After establishing a network communication send a message to the device for changing the IP address. That worked fine if my devices IP address is correct. But when I set a wrong IP address and subnet to the device. My application will never get any messages from the device. So I can't able communicate to the device and not able get the device and unable to change the IP address etc. Say example IP address of the device 20.1.1.1 Subnet Mask 255.0.0.0 And in my system that runs the application IP address 192.168.1.23 Subnet Mask 255.255.255.0 I tried the Lantronix device installation software with their Lantronix device in network. It listed the device from the network and I am able to change the IP address from their software. Any one know how this is done in this type of software? How I can search in network to find the device and change the IP address when its IP address is not in range? Which protocol they used to find the device?

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  • C# Detect Localhost Port Usage

    - by ThaKidd
    In advance, thank you for your advice. I am currently working on a program which uses Putty to create a SSH connection with a server that uses local port forwarding to enable a client, running my software, to access the service behind the SSH server via localhost. IE: client:20100 - Internet - Remote SSH server exposed via router/firewall - Local Intranet - Intranet Web POP3 Server:110. Cmd Line: "putty -ssh -2 -P 22 -C -L 20100:intranteIP:110 -pw sshpassword sshusername@sshserver" Client would use putty to create a SSH connection with the SSH server specifying in the connection string that it would like to tie port 110 of the Intranet POP3 Server to port 20100 on the client system. Therefore the client would be able to open up a mail client to localhost:20100 and interact with the Internal POP3 server over the SSH tunnel. The above is a general description. I already know what I am trying to do will work without a problem so am not looking for debate on the above. The question is this...How can I ensure the local port (I cannot use dynamic ports, so it must be static) on localhost is not being used or listened to by any other application? I am currently executing this code in my C# app: private bool checkPort(int port) { try { //Create a socket on the current IPv4 address Socket TestSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); // Create an IP end point IPEndPoint localIP = new IPEndPoint(IPAddress.Parse("127.0.0.1"), port); // Bind that port TestSocket.Bind(localIP); // Cleanup TestSocket.Close(); return false; } catch (Exception e) { // Exception occurred. Port is already bound. return true; } } I am currently calling this function starting with a specific port in a for loop to get the 'false' return at the first available port. The first port I try is actually being listened to by uTorrent. The above code does not catch this and my connection fails. What is the best method to ensure a port is truly free? I do understand some other program may grab the port during/after I have tested it. I just need to find something that will ensure it is not currently in use AT ALL when the test is executed. If there is a way to truly reserve the localhost port during the test, I would love to hear about it.

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  • How to migrate existing udp application to raw sockets

    - by osgx
    Hello Is there a tutorial for migration from plain udp sockets (linux, C99/C++, recv syscall is used) to the raw sockets? According to http://aschauf.landshut.org/fh/linux/udp_vs_raw/ch03s04.html raw socket is much faster than udp. Application is client-server. client is proprietary and must use exactly same procotol as it was with udp server. But server can be a bit faster with raw sockets. What parts of udp I must to implement in server? Is there a "quick migration" libraries?

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  • Neural Networks test cases

    - by Betamoo
    Does increasing the number of test cases in case of Precision Neural Networks may led to problems (like over-fitting for example)..? Does it always good to increase test cases number? Will that always lead to conversion ? If no, what are these cases.. an example would be better.. Thanks,

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  • Disaster Recovery Example

    Previously, I use to work for a small internet company that sells dental plans online. Our primary focus concerning disaster prevention and recovery is on our corporate website and private intranet site. We had a multiphase disaster recovery plan that includes data redundancy, load balancing, and off-site monitoring. Data redundancy is a key aspect of our disaster recovery plan. The first phase of this is to replicate our data to multiple database servers and schedule daily backups of the databases that are stored off site. The next phase is the file replication of data amongst our web servers that are also backed up daily by our collocation. In addition to the files located on the server, files are also stored locally on development machines, and again backed up using version control software. Load balancing is another key aspect of our disaster recovery plan. Load balancing offers many benefits for our system, better performance, load distribution and increased availability. With our servers behind a load balancer our system has the ability to accept multiple requests simultaneously because the load is split between multiple servers. Plus if one server is slow or experiencing a failure the traffic is diverted amongst the other servers connected to the load balancer allowing the server to get back online. The final key to our disaster recovery plan is off-site monitoring that notifies all IT staff of any outages or errors on the main website encountered by the monitor. Messages are sent by email, voicemail, and SMS. According to Disasterrecovery.org, disaster recovery planning is the way companies successfully manage crises with minimal cost and effort and maximum speed compared to others that are forced to make decision out of desperation when disasters occur. In addition Sun Guard stated in 2009 that the first step in disaster recovery planning is to analyze company risks and factor in fixed costs for things like hardware, software, staffing and utilities, as well as indirect costs, such as floor space, power protection, physical and information security, and management. Also availability requirements need to be determined per application and system as well as the strategies for recovery.

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  • Routing algorithm

    - by isaac
    Hello, I'm giving a presentation about computer routing and I want to make a good analogy with a real-world situation. However, I could not find it. Do you have in mind any of the situations like the computer routing. If yes, could you please provide me with it

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  • Python: How to transfer varrying length arrays over a network connection

    - by Devin
    Hi, I need to transfer an array of varying length in which each element is a tuple of two integers. As an example: path = [(1,1),(1,2)] path = [(1,1),(1,2),(2,2)] I am trying to use pack and unpack, however, since the array is of varying length I don't know how to create a format such that both know the format. I was trying to turn it into a single string with delimiters, such as: msg = 1&1~1&2~ sendMsg = pack("s",msg) or sendMsg = pack("s",str(msg)) on the receiving side: path = unpack("s",msg) but that just prints 1 in this case. I was also trying to send 4 integers as well, which send and receive fine, so long as I don't include the extra string representing the path. sendMsg = pack("hhhh",p.direction[0],p.direction[1],p.id,p.health) on the receive side: x,y,id,health = unpack("hhhh",msg) The first was for illustration as I was trying to send the format "hhhhs", but either way the path doesn't come through properly. Thank-you for your help. I will also be looking at sending a 2D array of ints, but I can't seem to figure out how to send these more 'complex' structures across the network. Thank-you for your help.

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  • How can I share the TV card on my home network? with a solution like `ln -s`?

    - by Boris
    My environment: - 2 PCs, a desktop and a laptop, both on Oneiric - they are connected together by ethernet wire - nfs-common is installed and configured: the desktop is the server - a TV tuner card is installed on the desktop, I can watch the French TNT TV with the software Me-TV It works fine, TV on desktop, and my network too: I share folders thanks to NFS. But I would like more: how can I share my TV tuner card from the desktop and be able to watch TV on the laptop too? If possible I would like a solution that allows me to keep using the software Me-TV, on both PCs. I bet that there is a solution to create a fake TV card on the 2nd PC. Something like ln -s on /dev/dvb/adapter0/.

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  • Internet Protocol Suite: Transition Control Protocol (TCP) vs. User Datagram Protocol (UDP)

    How do we communicate over the Internet?  How is data transferred from one machine to another? These types of act ivies can only be done by using one of two Internet protocols currently. The collection of Internet Protocol consists of the Transition Control Protocol (TCP) and the User Datagram Protocol (UDP).  Both protocols are used to send data between two network end points, however they both have very distinct ways of transporting data from one endpoint to another. If transmission speed and reliability is the primary concern when trying to transfer data between two network endpoints then TCP is the proper choice. When a device attempts to send data to another endpoint using TCP it creates a direct connection between both devices until the transmission has completed. The direct connection between both devices ensures the reliability of the transmission due to the fact that no intermediate devices are needed to transfer the data. Due to the fact that both devices have to continuously poll the connection until transmission has completed increases the resources needed to perform the transmission. An example of this type of direct communication can be seen when a teacher tells a students to do their homework. The teacher is talking directly to the students in order to communicate that the homework needs to be done.  Students can then ask questions about the assignment to ensure that they have received the proper instructions for the assignment. UDP is a less resource intensive approach to sending data between to network endpoints. When a device uses UDP to send data across a network, the data is broken up and repackaged with the destination address. The sending device then releases the data packages to the network, but cannot ensure when or if the receiving device will actually get the data.  The sending device depends on other devices on the network to forward the data packages to the destination devices in order to complete the transmission. As you can tell this type of transmission is less resource intensive because not connection polling is needed,  but should not be used for transmitting data with speed or reliability requirements. This is due to the fact that the sending device can not ensure that the transmission is received.  An example of this type of communication can be seen when a teacher tells a student that they would like to speak with their parents. The teacher is relying on the student to complete the transmission to the parents, and the teacher has no guarantee that the student will actually inform the parents about the request. Both TCP and UPD are invaluable when attempting to send data across a network, but depending on the situation one protocol may be better than the other. Before deciding on which protocol to use an evaluation for transmission speed, reliability, latency, and overhead must be completed in order to define the best protocol for the situation.  

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  • Throttle connections to web service if load gets too high?

    - by Joseph Turian
    I have a web site that communicates via XMLRPC with an XMLRPC server web service. (The web service is written in Python using xmlrpclib.) I believe that xmlrpclib will block while it is handling one request. So if there are three users with an xmlrpclib request ahead of you, your response takes four times as long. How do I handle it if I receive too many XMLRPC requests and the web service gets bogged down and has slow response time? If I am getting slashdotted, my preferred behavior is that the first users get good response times and everyone else is told to come back later. I think this is superior to giving everyone terrible response times. How do I create this behavior? Is this called load-balancing? I am not actually balancing though, until I have multiple servers.

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  • Network Load Balancing, intermittent port problem

    - by Jimmy Chandra
    Trying to troubleshoot an intermittent problem. I think it might be related to an NLB issue. We are using Windows Network Load Balancing to balance load for our multiserver SharePoint front ends. Say... Web Front End 1 IP is 192.168.1.100 and Web Front End 2 IP is 192.168.1.101, the NLB is setup to load balance both WFE servers on any incoming traffic to the IP 192.168.1.200. Sometimes we got an intermittent issue where when we try to access the SharePoint site using 192.168.1.200:8080 (say the site is set up to run on port 8080) from a remote client, it will display page not found. Pinging the 192.168.1.200 will give responses, but when trying to telnet to 192.168.1.200:8080 it just won't connect. However, browsing the SharePoint site directly on individual WFE (192.168.1.100 and 192.168.1.101) show no problem whatsoever. My guess also (we didn't get a chance to try it yet, but I think it should work), if I try connecting remotely to individual server, it will respond just fine. But any attempt on trying to connect using the virtual IP (192.168.1.200) will fail miserably. Funny thing is, after a while it will return back to normal. Anyone had similar experience with this type of problem while implementing NLB before? We are doing this in a virtual environment.

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  • Why do my backup fail when I target a network share hosted by a Synology DS211 disk station?

    - by Larry
    My backups are failing when I try to use a network share hosted by a Synology DS211 disk station. They work fine if I target a different network share (i.e. \server1\data\larry). When I run the following command: Wbadmin start backup -backupTarget:\\diskstation\backup-larry -include:C: This is what I get: wbadmin 1.0 - Backup command-line tool (C) Copyright 2004 Microsoft Corp. Note: The backed up data cannot be securely protected at this destination. Backups stored on a remote shared folder might be accessible by other people on the network. You should only save your backups to a location where you trust the other users who have access to the location or on a network that has additional security precautions in place. Retrieving volume information... This will back up volume WIN7(C:) to \\diskstation\backup-larry. Do you want to start the backup operation? [Y] Yes [N] No y Note: The list of volumes included for backup does not include all the volumes that contain operating system components. This backup cannot be used to perform a system recovery. However, you can recover other items if the destination media type supports it. The backup operation to \\diskstation\backup-larry is starting. Creating a shadow copy of the volumes specified for backup... Creating a shadow copy of the volumes specified for backup... The backup operation stopped before completing. Summary of the backup operation: ------------------ The backup operation stopped before completing. Detailed error: Access is denied. Windows Backup failed to write the file: '<backup location>\WindowsImageBackup\<Computer Name>\MediaId'. Access is denied. The backup creates the following path \\diskstation\backup-larry\WindowsImageBackup\LARRY-MYDOMAIN\ but its empty. I definitely have read/write access on the target directory (\diskstation\backup-larry). I have verified this by looking at the permission and by actually copying files to this location. Any suggestions?

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  • haproxy - pass original / remote ip in tcp mode

    - by Vito Botta
    I've got haproxy set up with keepalived for load balancing and ip failover of a percona cluster, and since it works great I'd like to use the same lb / failover for another service/daemon. I've configured haproxy this way: listen my_service 0.0.0.0:4567 mode tcp balance leastconn option tcpka contimeout 500000 clitimeout 500000 srvtimeout 500000 server host1 xxx.xxx.xxx.xx1:4567 check port 4567 inter 5000 rise 3 fall 3 server host2 xxx.xxx.xxx.xx2:4567 check port 4567 inter 5000 rise 3 fall 3 The load balancing works fine, but the service sees the IP of the load balancer instead of the actual IPs of the clients. In http mode it's quite easy to have haproxy pass along the remote IP, but how do I do in tcp mode? This is critical due to the nature of the service I need to load balance. Thanks! Vito

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  • Network Load Balancing, intermittent port problem on Windows Server 2008

    - by Jimmy Chandra
    Trying to troubleshoot an intermittent problem on a Windows Server 2008 NLB. I think it might be related to an NLB issue. We are using Windows Network Load Balancing to balance load for our multiserver SharePoint front ends. Say... Web Front End 1 IP is 192.168.1.100 and Web Front End 2 IP is 192.168.1.101, the NLB is setup to load balance both WFE servers on any incoming traffic to the IP 192.168.1.200. Sometimes we got an intermittent issue where when we try to access the SharePoint site using 192.168.1.200:8080 (say the site is set up to run on port 8080) from a remote client, it will display page not found. Pinging the 192.168.1.200 will give responses, but when trying to telnet to 192.168.1.200:8080 it just won't connect. However, browsing the SharePoint site directly on individual WFE (192.168.1.100 and 192.168.1.101) show no problem whatsoever. My guess also (we didn't get a chance to try it yet, but I think it should work), if I try connecting remotely to individual server, it will respond just fine. But any attempt on trying to connect using the virtual IP (192.168.1.200) will fail miserably. Funny thing is, after a while it will return back to normal. Anyone had similar experience with this type of problem while implementing NLB before? We are doing this in a virtual environment.

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  • Working WCF WebServices with NLB server

    - by gguth
    Im starting the architecture of a new project using WCF, but im not the right person to make some network considerations, so im doing some research but cannot find the answers to these questions: We´ll host the WCF service in a common Windows Service app in 2 servers and we´ll have another server to make the Load-Balancing job using the WNLB. The fact that we are hosting the WCF in a Windows Service app can disturb the NLB job? Before my research i thought the load balancing was tought to configure, but with NLB it seems to be very simple, its really that simple? Note: The binding will be basicHttpBinding

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