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  • How to transfer data between two netowks efficiently

    - by Tono Nam
    I will like to transfer files between two places over the internet. Right now I have a VPN and I am able to browse, download and transfer files. So my question is not really how to transfer the files; Instead, I will like to use the most efficient approach because the two places constantly share a lot of data. The reason why I want to get rid of the vpn is because it is two slow. Having high upload speed is very expensive/impossible on residential places so I will like to use a different approach. I was thinking about using programs such as http://www.dropbox.com . The problem with dropbox is it only enables 2 GB of storage in order for it to be free. I think the deals they offer are ok and I might be willing to pay to get that increase in speed. But I am concerned with the speed of transferring data. Dropbox will upload the file to their server then send it from the server to the other location. I will like it even faster lol. Anyways I was thinking why not create a program my self. This is the algorithm that I was thinking let me know if it sounds to crazy. (remember my goal is to transfer files as fastest as possible) Things that I will use in this algorithm: Server on the internet called S ( has fast download and upload speed. I pay to host a website and some services in there. I want to take advantage of it) Client A on location 1 Client B on location 2 So lets say on location 1 20 large files are created and need to be transferred to location 2. Client A compresses the files with the highest compression ratio possible. Client A starts sending data via UDP to client B. Because I am using UDP I will include the sequence number on each package. Have server S help speed up things. For example every time a package is lost we can use Server S to inform client A that it needs to resend a package. Anyways I think this approach will increase the transfer rate. I do not know if it is possible to start sending data meanwhile it is being compressed. Also if it is possible to start decompressing data even if we are not done receiving all the info. Maybe it will be faster to start sending the files right away without compressing. If I knew that I will always be sending large text files then I will obviously use the compression. I need this as a general algorithm. So i guess my question is should using UDP over TCP could increase performance by using an extra server to keep track of lost packages? and How should I compress files before sending? compressing a 1 GB file with the highest compression ration takes about 1 hour! I will like to take advantage of that time by sending it meanwhile it is compressed.

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  • "Possible SYN flooding" in log despite low number of SYN_RECV connections

    - by al4
    Recently we had an apache server which was responding very slowly due to SYN flooding. The workaround for this was to enable tcp_syncookies (net.ipv4.tcp_syncookies=1 in /etc/sysctl.conf). I posted a question about this here if you want more background. After enabling syncookies we started seeing the following message in /var/log/messages approximately every 60 seconds: [84440.731929] possible SYN flooding on port 80. Sending cookies. Vinko Vrsalovic informed me that this means the syn backlog is getting full, so I raised tcp_max_syn_backlog to 4096. At some point I also lowered tcp_synack_retries to 3 (down from the default of 5) by issuing sysctl -w net.ipv4.tcp_synack_retries=3. After doing this, the frequency seemed to drop, with the interval of the messages varying between roughly 60 and 180 seconds. Next I issued sysctl -w net.ipv4.tcp_max_syn_backlog=65536, but am still getting the message in the log. Throughout all this I've been watching the number of connections in SYN_RECV state (by running watch --interval=5 'netstat -tuna |grep "SYN_RECV"|wc -l'), and it never goes higher than about 240, much much lower than the size of the backlog. Yet I have a Red Hat server which hovers around 512 (limit on this server is the default of 1024). Are there any other tcp settings which would limit the size of the backlog or am I barking up the wrong tree? Should the number of SYN_RECV connections in netstat -tuna correlate to the size of the backlog? Update As best I can tell I'm dealing with legitimate connections here, netstat -tuna|wc -l hovers around 5000. I've been researching this today and found this post from a last.fm employee, which has been rather useful. I've also discovered that the tcp_max_syn_backlog has no effect when syncookies are enabled (as per this link) So as a next step I set the following in sysctl.conf: net.ipv4.tcp_syn_retries = 3 # default=5 net.ipv4.tcp_synack_retries = 3 # default=5 net.ipv4.tcp_max_syn_backlog = 65536 # default=1024 net.core.wmem_max = 8388608 # default=124928 net.core.rmem_max = 8388608 # default=131071 net.core.somaxconn = 512 # default = 128 net.core.optmem_max = 81920 # default = 20480 I then setup my response time test, ran sysctl -p and disabled syncookies by sysctl -w net.ipv4.tcp_syncookies=0. After doing this the number of connections in the SYN_RECV state still remained around 220-250, but connections were starting to delay again. Once I noticed these delays I re-enabled syncookies and the delays stopped. I believe what I was seeing was still an improvement from the initial state, however some requests were still delayed which is much worse than having syncookies enabled. So it looks like I'm stuck with them enabled until we can get some more servers online to cope with the load. Even then, I'm not sure I see a valid reason to disable them again as they're only sent (apparently) when the server's buffers get full. But the syn backlog doesn't appear to be full with only ~250 connections in the SYN_RECV state! Is it possible that the SYN flooding message is a red herring and it's something other than the syn_backlog that's filling up? If anyone has any other tuning options I haven't tried yet I'd be more than happy to try them out, but I'm starting to wonder if the syn_backlog setting isn't being applied properly for some reason.

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  • Page allocation failures on iSCSI storage

    - by Dave
    We have a CentOS 6.3 iscsi server (16GB RAM) running on Infiniband bus (ipoib). When the load is high I can see multiple errors: Sep 3 23:22:20 stor4 kernel: tgtd: page allocation failure. order:2, mode:0x20 Sep 3 23:22:20 stor4 kernel: Pid: 3637, comm: tgtd Not tainted 2.6.32 #1 Sep 3 23:22:20 stor4 kernel: Call Trace: Sep 3 23:22:20 stor4 kernel: [] ? __alloc_pages_nodemask+0x77f/0x940 Sep 3 23:22:20 stor4 kernel: [] ? kmem_getpages+0x62/0x170 Sep 3 23:22:20 stor4 kernel: [] ? fallback_alloc+0x1ba/0x270 Sep 3 23:22:20 stor4 kernel: [] ? cache_grow+0x2cf/0x320 Sep 3 23:22:20 stor4 kernel: [] ? ____cache_alloc_node+0x99/0x160 Sep 3 23:22:20 stor4 kernel: [] ? pskb_expand_head+0x64/0x270 Sep 3 23:22:20 stor4 kernel: [] ? __kmalloc+0x189/0x220 Sep 3 23:22:20 stor4 kernel: [] ? pskb_expand_head+0x64/0x270 Sep 3 23:22:20 stor4 kernel: [] ? __pskb_pull_tail+0x2aa/0x360 Sep 3 23:22:20 stor4 kernel: [] ? tcp_init_tso_segs+0x37/0x50 Sep 3 23:22:20 stor4 kernel: [] ? dev_queue_xmit+0x4bb/0x6f0 Sep 3 23:22:20 stor4 kernel: [] ? neigh_connected_output+0xbd/0x100 Sep 3 23:22:20 stor4 kernel: [] ? ip_finish_output+0x237/0x310 Sep 3 23:22:20 stor4 kernel: [] ? ip_output+0xb8/0xc0 Sep 3 23:22:20 stor4 kernel: [] ? __ip_local_out+0x9f/0xb0 Sep 3 23:22:20 stor4 kernel: [] ? ip_local_out+0x25/0x30 Sep 3 23:22:20 stor4 kernel: [] ? ip_queue_xmit+0x190/0x420 Sep 3 23:22:20 stor4 kernel: [] ? sock_aio_write+0x167/0x180 Sep 3 23:22:20 stor4 kernel: [] ? tcp_transmit_skb+0x3fe/0x7b0 Sep 3 23:22:20 stor4 kernel: [] ? tcp_write_xmit+0x1fb/0xa20 Sep 3 23:22:20 stor4 kernel: [] ? __tcp_push_pending_frames+0x30/0xe0 Sep 3 23:22:20 stor4 kernel: [] ? tcp_push_pending_frames+0x33/0x40 Sep 3 23:22:20 stor4 kernel: [] ? do_tcp_setsockopt+0x3d6/0x480 Sep 3 23:22:20 stor4 kernel: [] ? tcp_setsockopt+0x2a/0x30 Sep 3 23:22:20 stor4 kernel: [] ? sock_common_setsockopt+0x14/0x20 Sep 3 23:22:20 stor4 kernel: [] ? sys_setsockopt+0x7f/0xe0 Sep 3 23:22:20 stor4 kernel: [] ? system_call_fastpath+0x16/0x1b Sep 3 23:22:20 stor4 kernel: Mem-Info: Sep 3 23:22:20 stor4 kernel: Node 0 DMA per-cpu: Sep 3 23:22:20 stor4 kernel: CPU 0: hi: 0, btch: 1 usd: 0 Sep 3 23:22:20 stor4 kernel: CPU 1: hi: 0, btch: 1 usd: 0 Sep 3 23:22:20 stor4 kernel: CPU 2: hi: 0, btch: 1 usd: 0 Sep 3 23:22:20 stor4 kernel: CPU 3: hi: 0, btch: 1 usd: 0 Sep 3 23:22:20 stor4 kernel: Node 0 DMA32 per-cpu: Sep 3 23:22:20 stor4 kernel: CPU 0: hi: 186, btch: 31 usd: 183 Sep 3 23:22:20 stor4 kernel: CPU 1: hi: 186, btch: 31 usd: 23 Sep 3 23:22:20 stor4 kernel: CPU 2: hi: 186, btch: 31 usd: 183 Sep 3 23:22:20 stor4 kernel: CPU 3: hi: 186, btch: 31 usd: 181 Sep 3 23:22:20 stor4 kernel: Node 0 Normal per-cpu: Sep 3 23:22:20 stor4 kernel: CPU 0: hi: 186, btch: 31 usd: 171 Sep 3 23:22:20 stor4 kernel: CPU 1: hi: 186, btch: 31 usd: 29 Sep 3 23:22:20 stor4 kernel: CPU 2: hi: 186, btch: 31 usd: 32 Sep 3 23:22:20 stor4 kernel: CPU 3: hi: 186, btch: 31 usd: 32 Sep 3 23:22:20 stor4 kernel: active_anon:1875 inactive_anon:2473 isolated_anon:0 Sep 3 23:22:20 stor4 kernel: active_file:1243637 inactive_file:2505055 isolated_file:0 Sep 3 23:22:20 stor4 kernel: unevictable:0 dirty:268338 writeback:0 unstable:0 Sep 3 23:22:20 stor4 kernel: free:86050 slab_reclaimable:132377 slab_unreclaimable:23744 Sep 3 23:22:20 stor4 kernel: mapped:1293 shmem:222 pagetables:720 bounce:0 Sep 3 23:22:20 stor4 kernel: Node 0 DMA free:15732kB min:124kB low:152kB high:184kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15332kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes Sep 3 23:22:20 stor4 kernel: lowmem_reserve[]: 0 2172 16060 16060 Sep 3 23:22:20 stor4 kernel: Node 0 DMA32 free:107544kB min:18268kB low:22832kB high:27400kB active_anon:468kB inactive_anon:2364kB active_file:566208kB inactive_file:976112kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2224900kB mlocked:0kB dirty:96816kB writeback:0kB mapped:908kB shmem:12kB slab_reclaimable:176940kB slab_unreclaimable:968kB kernel_stack:64kB pagetables:192kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no Sep 3 23:22:20 stor4 kernel: lowmem_reserve[]: 0 0 13887 13887 Sep 3 23:22:20 stor4 kernel: Node 0 Normal free:220924kB min:116772kB low:145964kB high:175156kB active_anon:7032kB inactive_anon:7528kB active_file:4408340kB inactive_file:9044108kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:14220800kB mlocked:0kB dirty:976536kB writeback:0kB mapped:4264kB shmem:876kB slab_reclaimable:352568kB slab_unreclaimable:94008kB kernel_stack:2048kB pagetables:2688kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no Sep 3 23:22:20 stor4 kernel: lowmem_reserve[]: 0 0 0 0 Sep 3 23:22:20 stor4 kernel: Node 0 DMA: 1*4kB 0*8kB 1*16kB 1*32kB 1*64kB 0*128kB 1*256kB 0*512kB 1*1024kB 1*2048kB 3*4096kB = 15732kB Sep 3 23:22:20 stor4 kernel: Node 0 DMA32: 16305*4kB 4381*8kB 353*16kB 8*32kB 1*64kB 1*128kB 0*256kB 1*512kB 1*1024kB 0*2048kB 0*4096kB = 107900kB Sep 3 23:22:20 stor4 kernel: Node 0 Normal: 14548*4kB 14808*8kB 2420*16kB 31*32kB 5*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 1*4096kB = 220784kB Sep 3 23:22:20 stor4 kernel: 3748822 total pagecache pages Sep 3 23:22:20 stor4 kernel: 0 pages in swap cache Sep 3 23:22:20 stor4 kernel: Swap cache stats: add 0, delete 0, find 0/0 Sep 3 23:22:20 stor4 kernel: Free swap = 975864kB Sep 3 23:22:20 stor4 kernel: Total swap = 975864kB Sep 3 23:22:20 stor4 kernel: 4194303 pages RAM Sep 3 23:22:20 stor4 kernel: 126915 pages reserved Sep 3 23:22:20 stor4 kernel: 3753534 pages shared Sep 3 23:22:20 stor4 kernel: 213500 pages non-shared TCP stack and VM config: net.core.rmem_max = 83886080 net.core.wmem_max = 83886080 net.core.rmem_default = 65536 net.core.wmem_default = 65536 net.ipv4.tcp_rmem = 40960 1048560 4194304 net.ipv4.tcp_wmem = 40960 196608 4194304 net.ipv4.tcp_mem = 16388608 16388608 16388608 vm.min_free_kbytes=135168 Additional tweaks: /sbin/blockdev --setra 16384 /dev/sdb echo 2048 /sys/block/sdb/queue/nr_requests Where might the problem be? Thank you.

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  • How to solve "The ChannelDispatcher is unable to open its IChannelListener" error?

    - by kyrisu
    Hi, I'm trying to communicate between WCF hosted in Windows Service and my service GUI. The problem is when I'm trying to execute OperationContract method I'm getting "The ChannelDispatcher at 'net.tcp://localhost:7771/MyService' with contract(s) '"IContract"' is unable to open its IChannelListener." My app.conf looks like that: <configuration> <system.serviceModel> <bindings> <netTcpBinding> <binding name="netTcpBinding"> <security> <transport protectionLevel="EncryptAndSign" /> </security> </binding> </netTcpBinding> </bindings> <behaviors> <serviceBehaviors> <behavior name="MyServiceBehavior"> <serviceMetadata httpGetEnabled="true" httpGetUrl="http://localhost:7772/MyService" /> <serviceDebug includeExceptionDetailInFaults="true" /> </behavior> </serviceBehaviors> </behaviors> <services> <service behaviorConfiguration="MyServiceBehavior" name="MyService.Service"> <endpoint address="net.tcp://localhost:7771/MyService" binding="netTcpBinding" bindingConfiguration="netTcpBinding" name="netTcp" contract="MyService.IContract" /> </service> </services> </system.serviceModel> Port 7771 is listening (checked using netstat) and svcutil is able to generate configs for me. Any suggestions would be appreciated. Stack trace from exception Server stack trace: at System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message reply, MessageFault fault, String action, MessageVersion version, FaultConverter faultConverter) at System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime operation, ProxyRpc& rpc) at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs) at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation) at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message) There's one inner exeption (but not under Exeption.InnerExeption but under Exeption.Detail.InnerExeption - ToString() method doesn't show that) A registration already exists for URI 'net.tcp://localhost:7771/MyService'. But my service have specified this URI only in app.config file nowhere else. In entire solution this URI apears in server once and client once.

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  • WCF Blocking problem with mutiple clients!!

    - by Marcel
    Hi I seem to have a blocking issue with WCF. Say I have two users and each have created their own instance of a class exposed on a WCF host using net.tcp with endpoint something like this "net.tcp://localhost:32000/SymHost/". The class is PerSession context and concurrency is reentrant. The class exposes two methods Alive() which return a bool of true straight away and an AliveWait which I inserted which does a Thread.Sleep for 4 seconds before returning true (testing purposes). Now client 1 calls AliveWait() during which time he is blocked which is fair enough but then if client 2 makes a call to Alive() on its own instance he has to wait until client 1's call is returned - this behaviour is not what I would have expected? I would have expected client 2 to carry on as if nothing has happened or is this to do with the fact that they both share the same endpoint? Can anyone explain what is going on and how I can make sure that client 2 can call its own instance uninterrupted? Any help much appreciated!

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  • Async Socket Listener on separate thread - VB.net

    - by TheHockeyGeek
    I am trying to use the code from Microsoft for an Async Socket connection. It appears the listener runs in the main thread locking the GUI. I am new at both socket connections and multi-threading all at the same time. Having a hard time getting my mind wrapped around this all at once. The code used is at http://msdn.microsoft.com/en-us/library/fx6588te.aspx Using this example, how can I move the listener to its own thread? Public Shared Sub Main() ' Data buffer for incoming data. Dim bytes() As Byte = New [Byte](1023) {} ' Establish the local endpoint for the socket. Dim ipHostInfo As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName()) Dim ipAddress As IPAddress = ipHostInfo.AddressList(1) Dim localEndPoint As New IPEndPoint(ipAddress, 11000) ' Create a TCP/IP socket. Dim listener As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp) ' Bind the socket to the local endpoint and listen for incoming connections. listener.Bind(localEndPoint) listener.Listen(100)

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  • How do I handle partial write completions from overlapped I/O using I/O Completion Ports

    - by Poni
    On Windows I/O completion ports, say I do this: void function() { WSASend("1111"); // A WSASend("2222"); // B WSASend("3333"); // C } If I got a "write-complete" that says 3 bytes of WSASend() A were sent, is it possible that right after that I'll get a "write-complete" that tells me that some or all of B & C were sent, or will TCP will hold them until I re-issue a WSASend() call with the rest of A's data? Or will TCP complete it automatically?

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  • How to recive more than 65000 bytes in C++ socket using recv()

    - by Mr.Cool
    I am developing a client server application (TCP) in Linux using C++. I want to send more than 65,000 bytes at the same time. In TCP, the maximum packet size is 65,635 bytes only. How can I send the entire bytes without loss? Following is my code at server side. //Receive the message from client socket if((iByteCount = recv(GetSocketId(), buffer, MAXRECV, MSG_WAITALL)) > 0) { printf("\n Received bytes %d\n", iByteCount); SetReceivedMessage(buffer); return LS_RESULT_OK; } If I use MSG_WAITALL it takes a long time to receive the bytes so how can I set the flag to receive more than 10 lakhs bytes at time.

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  • Sockets: RAW or STREAM

    - by user1415536
    May be the question is a bit stupid, but I'll ask it. I read a lot about raw sockets in network, have seen several examples. So, basically with raw sockets it's possible to build own stack of headers, like stack = IP + TCP/UDP + OWN_HEADER. My question is, is it possible to get some kind of ready frame of first two(IP + TCP/UDP) from the linux kernel and then just append own header to them? The operating system in question is linux and the language is C. I cannot find any function which can do such a thing, but may be I'm digging in a wrong direction.

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  • Is a live internet connection required for push notification?

    - by Heshan Perera
    This maybe a silly question, but I need confirmation and I have no one else to ask. I am trying to understand the implications of implementing my own push notification for android mobile devices. This requires a continuous TCP connection to a server, though most of the time it will be idle. My assumption is that, even when idle, for the server to be able to push data to the client through the TCP connection, an active internet connection will always be required, and if the connection is disrupted (i.e. the user switches the connection off) this push will no longer be possible. Is this assumption correct ?

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  • When to use Nginx PHP Fast CGI with a TCP socket instead of a UNIX socket?

    - by user64204
    I've followed this guide to setup PHP in FastCGI mode with Nginx. This guide describes 2 ways of doing it: TCP socket and UNIX socket. I've ran some Apache Benchmark on my locale machine and here are the results: Below tests ran multiple times to get better average statistics: $ ab -c 200 -n 100000 http://.... APACHE: 1800 req/sec NGINX (TCP socket): 2500 req/sec NGINX (UNIX socket): 15000 req/sec As far as I understand, there is overhead with using a TCP socket rather than a UNIX socket, hence the better performance with the latter. However I was not expecting such a performance difference given that the TCP socket is on the localhost, and therefore would like to ask the following question: Q: Given the huge performance gain with using a UNIX socket, what are the configuration scenarios where it would make sense to use a TCP socket instead?

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  • Nonblocking Tcp server

    - by hoodoos
    It's not a question really, i'm just looking for some guidelines :) I'm currently writing some abstract tcp server which should use as low number of threads as it can. Currently it works this way. I have a thread doing listening and some worker threads. Listener thread is just sits and wait for clients to connect I expect to have a single listener thread per server instance. Worker threads are doing all read/write/processing job on clients socket. So my problem is in building efficient worker process. And I came to some problem I can't really solve yet. Worker code is something like that(code is really simple just to show a place where i have my problem): List<Socket> readSockets = new List<Socket>(); List<Socket> writeSockets = new List<Socket>(); List<Socket> errorSockets = new List<Socket>(); while( true ){ Socket.Select( readSockets, writeSockets, errorSockets, 10 ); foreach( readSocket in readSockets ){ // do reading here } foreach( writeSocket in writeSockets ){ // do writing here } // POINT2 and here's the problem i will describe below } it works all smothly accept for 100% CPU utilization because of while loop being cycling all over again, if I have my clients doing send-receive-disconnect routine it's not that painful, but if I try to keep alive doing send-receive-send-receive all over again it really eats up all CPU. So my first idea was to put a sleep there, I check if all sockets have their data send and then putting Thread.Sleep in POINT2 just for 10ms, but this 10ms later on produces a huge delay of that 10ms when I want to receive next command from client socket.. For example if I don't try to "keep alive" commands are being executed within 10-15ms and with keep alive it becomes worse by atleast 10ms :( Maybe it's just a poor architecture? What can be done so my processor won't get 100% utilization and my server to react on something appear in client socket as soon as possible? Maybe somebody can point a good example of nonblocking server and architecture it should maintain?

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  • Non-blocking TCP buffer issues.

    - by Poni
    Hi! I think I'm in a problem. I have two TCP apps connected to each other which use winsock I/O completion ports to send/receive data (non-blocking sockets). Everything works just fine until there's a data transfer burst. The sender starts sending incorrect/malformed data. I allocate the buffers I'm sending on the stack, and if I understand correctly, that's a wrong to do, because these buffers should remain as I sent them until I get the "write complete" notification from IOCP. Take this for example: void some_function() { char cBuff[1024]; // filling cBuff with some data WSASend(...); // sending cBuff, non-blocking mode // filling cBuff with other data WSASend(...); // again, sending cBuff // ..... and so forth! } If I understand correctly, each of these WSASend() calls should have its own unique buffer, and that buffer can be reused only when the send completes. Correct? Now, what strategies can I implement in order to maintain a big sack of such buffers, how should I handle them, how can I avoid performance penalty, etc'? And, if I am to use buffers that means I should copy the data to be sent from the source buffer to the temporary one, thus, I'd set SO_SNDBUF on each socket to zero, so the system will not re-copy what I already copied. Are you with me? Please let me know if I wasn't clear.

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  • Android: Streaming audio over TCP Sockets

    - by user299988
    Hi, For my app, I need to record audio from MIC on an Android phone, and send it over TCP to the other android phone, where it needs to be played. I am using AudioRecord and AudioTrack class. This works great with a file - write audio to the file using DataOutputStream, and read from it using DataInputStream. However, if I obtain the same stream from a socket instead of a File, and try writing to it, I get an exception. I am at a loss to understand what could possibly be going wrong. Any help would be greatly appreciated. EDIT: The problem is same even if I try with larger buffer sizes (65535 bytes, 160000 bytes). This is the code: Recorder: int bufferSize = AudioRecord.getMinBufferSize(11025, , AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT); AudioRecord recordInstance = new AudioRecord(MediaRecorder.AudioSource.MIC, 11025, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize); byte[] tempBuffer = new byte[bufferSize]; recordInstance.startRecording(); while (/*isRecording*/) { bufferRead = recordInstance.read(tempBuffer, 0, bufferSize); dataOutputStreamInstance.write(tempBuffer); } The DataOutputStream above is obtained as: BufferedOutputStream buff = new BufferedOutputStream(out1); //out1 is the socket's outputStream DataOutputStream dataOutputStreamInstance = new DataOutputStream (buff); Could you please have a look, and let me know what is it that I could be doing wrong here? Thanks,

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  • Non-blocking TCP connection issues.

    - by Poni
    Hi! I think I'm in a problem. I have two TCP apps connected to each other which use winsock I/O completion ports to send/receive data (non-blocking sockets). Everything works just fine until there's a data transfer burst. The sender starts sending incorrect/malformed data. I allocate the buffers I'm sending on the stack, and if I understand correctly, that's a wrong to do, because these buffers should remain as I sent them until I get the "write complete" notification from IOCP. Take this for example: void some_function() { char cBuff[1024]; // filling cBuff with some data WSASend(...); // sending cBuff, non-blocking mode // filling cBuff with other data WSASend(...); // again, sending cBuff // ..... and so forth! } If I understand correctly, each of these WSASend() calls should have its own unique buffer, and that buffer can be reused only when the send completes. Correct? Now, what strategies can I implement in order to maintain a big sack of such buffers, how should I handle them etc'? And, if I am to use buffers that means I should copy the data to be sent from the source buffer to the temporary one, thus, I'd set SO_SNDBUF on each socket to zero, so the system will not re-copy what I already copied. Are you with me? Please let me know if I wasn't clear.

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  • Using boost asio for pub/sub style tcp in a game loop

    - by unohoo
    I have been reading through the boost asio documentation for a couple of hours now, and while I think the documentation is really great, I am still left a bit confused on how to implement the system that I need. I have to stream info, from a game engine, to a list of computers over tcp. One snag is that, unlike traditional pub/sub, the computer that does the distribution of info is actually the computer that has to connect to the subscribers as well (instead of the subscribers registering with the publisher). This is done via a config file - a list of ip's/ports along with the data that they each require. The subscribers listen, but do not know the ip of the publisher. (As a side note, I'm quite new to network programming, so maybe I'm missing something .. but it's strange that I do not find much information regarding this style of "inverted" client-server model..) I am looking for suggestions for the implementation of such a system using boost asio. Of course I have to integrate the networking into an already existing engine, so with regards to that: What would be a good way to handle messages being sent to multiple computers every frame? Use async_write, call io_service.run and then reset every frame? Would having io_service.run have its own thread be better? Or should I just use threads and use blocking writes?

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  • implementing a Intelligent File Transfer Software in java over TCP/IP

    - by whyjava
    Hello I am working on a proposal where we have to implement a software which can move files between one source to destination.The overall goal of this project is to create intelligent file transfer.This software will have three components :- 1) Broker : Broker is the module that communicates with other brokers, monitors files, moves files, retrieves configurations from the Configuration Manager, supplies process information for the monitor, archives files, writes all process data to log files and escalates issues if necessary 2) Configuration Manager :Configuration Manager is a web-based application used to configure and deploy the configuration to all brokers. 3) Monitor : Monitor is a web-based application used to monitor each Broker in the environment. This project has to be built up in java and protocol for file transfer in tcp/ip. Client does not want to use FTP. File Transfer seems very easy, until there are several processes who are waiting to pick the file up automatically. Several problems arise: How can we guarantee the file is received at the destination? If a file isn’t received the first time, we should try it again (even after a restart or power breakdown) ? How does the receiver knows the file that is received is complete? How can we transfer multiple files synchronously? How can we protect the bandwidth, so file transfer isn’t blocking other processes? How does one interoperate between multiple OS platforms? What about authentication? How can we monitor het workflow? Auditing / logging Archiving Can you please provide answer to some of these? Thanks

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  • Remoting connection over TCP

    - by Voyager Systems
    I've got a remoting server and client built. The server is set up as such: BinaryServerFormatterSinkProvider serverProv = new BinaryServerFormatterSinkProvider(); serverProv.TypeFilterLevel = TypeFilterLevel.Full; BinaryClientFormatterSinkProvider clientProv = new BinaryClientFormatterSinkProvider(); IDictionary props = new Hashtable(); props["port"] = port; TcpChannel channel = new TcpChannel( props, clientProv, serverProv ); ChannelServices.RegisterChannel( channel, false ); RemotingConfiguration.RegisterWellKnownServiceType( typeof( Controller ), "Controller", WellKnownObjectMode.Singleton ); The client is set up as such: ChannelServices.RegisterChannel( new TcpChannel( 0 ), false ); m_Controller = (Controller)RemotingServices.Connect( typeof( Controller ), "tcp://" + ip + ":2594/Controller" ); When I try to connect to the server from the same computer with the IP specified as 'localhost,' it connects fine. However, when I try to connect from a remote computer, not on the LAN, given the server's IP address, I receive the following exception on the client after a long wait: A connection attempt failed because the connected party did not properly respond after a period of time How can I resolve this? I'm sure it's a configuration problem because the ports are forwarded properly on the server and there is no firewall active. Thanks

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  • Iptables config breaks Java + Elastic Search communication

    - by Agustin Lopez
    I am trying to set up a firewall for a server hosting a java app and ES. Both are on the same server and communicate to each other. The problem I am having is that my firewall configuration prevents java from connecting to ES. Not sure why really.... I have tried lot of stuff like opening the port range 9200:9400 to the server ip without any luck but from what I know all communication inside the server should be allowed with this configuration. The idea is that ES should not be accessible from outside but it should be accessible from this java app and ES uses the port range 9200:9400. This is my iptables script: echo -e Deleting rules for INPUT chain iptables -F INPUT echo -e Deleting rules for OUTPUT chain iptables -F OUTPUT echo -e Deleting rules for FORWARD chain iptables -F FORWARD echo -e Setting by default the drop policy on each chain iptables -P INPUT DROP iptables -P OUTPUT ACCEPT iptables -P FORWARD DROP echo -e Open all ports from/to localhost iptables -A INPUT -i lo -j ACCEPT echo -e Open SSH port 22 with brute force security iptables -A INPUT -p tcp -m tcp --dport 22 -m state --state NEW -m recent --set --name SSH --rsource iptables -A INPUT -p tcp -m tcp --dport 22 -m recent --rcheck --seconds 30 --hitcount 4 --rttl --name SSH --rsource -j REJECT --reject-with tcp-reset iptables -A INPUT -p tcp -m tcp --dport 22 -m recent --rcheck --seconds 30 --hitcount 3 --rttl --name SSH --rsource -j LOG --log-prefix "SSH brute force " iptables -A INPUT -p tcp -m tcp --dport 22 -m recent --update --seconds 30 --hitcount 3 --rttl --name SSH --rsource -j REJECT --reject-with tcp-reset iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT echo -e Open NGINX port 80 iptables -A INPUT -p tcp --dport 80 -j ACCEPT echo -e Open NGINX SSL port 443 iptables -A INPUT -p tcp --dport 443 -j ACCEPT echo -e Enable DNS iptables -A INPUT -p tcp -m tcp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT iptables -A INPUT -p udp -m udp --sport 53 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT And I get this in the java app when this config is in place: org.elasticsearch.cluster.block.ClusterBlockException: blocked by: [SERVICE_UNAVAILABLE/1/state not recovered / initialized];[SERVICE_UNAVAILABLE/2/no master]; at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:292) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1185) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:304) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:300) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:195) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:700) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:760) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482) at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:403) Do any of you see any problem with this configuration and ES? Thanks in advance

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  • VPN pptp connection Unable to pass through linux iptables

    - by user221844
    I have set up a windows VPN server behind Linux - Ubuntu box that is working as firewall and proxy server. Now I want people from outside to be able to connect to the VPN server, but the connection is not being established and I get on the client an error 619. I have checked the problem on the internet and it seems a firewall issue. what should I do to make the connection established through the firewall? here is below the information about my setup Firewall-External-IF-IP: 172.16.1.100 Firewall-LAN-IF-IP: 192.168.1.1 VPN-Server-IP: 192.168.1.10 and below is my iptables file content: #Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *filter :INPUT ACCEPT [162000:140437619] :FORWARD ACCEPT [23282:27196133] :OUTPUT ACCEPT [185778:143961739] :LOGGING - [0:0] -A INPUT -p gre -j ACCEPT -A INPUT -s 192.168.1.10/32 -p tcp -m tcp --sport 1723 -j ACCEPT -A INPUT -s 192.168.1.10/32 -p udp -m udp --sport 1723 -j ACCEPT -A FORWARD -s 192.168.1.0/24 -o EXT_IF -j ACCEPT -A FORWARD -s 192.168.1.0/24 -i EXT_IF -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -d 192.168.1.10/32 -i EXT_IF -o INT_IF -p tcp -m tcp --dport 1723 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT -A FORWARD -s 192.168.1.10/32 -i INT_IF -o EXT_IF -p tcp -m tcp --sport 1723 -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -d 192.168.1.10/32 -i EXT_IF -o INT_IF -p gre -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT -A FORWARD -s 192.168.1.10/32 -i INT_IF -o EXT_IF -p gre -m state --state RELATED,ESTABLISHED -j ACCEPT -A OUTPUT -p gre -j ACCEPT -A OUTPUT -d 192.168.1.10/32 -p tcp -m tcp --dport 1723 -j ACCEPT -A OUTPUT -d 192.168.1.10/32 -p udp -m udp --dport 1723 -j ACCEPT COMMIT # Completed on Thu May 29 12:40:18 2014 # Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *nat :PREROUTING ACCEPT [17865:1053739] :INPUT ACCEPT [5490:357281] :OUTPUT ACCEPT [3723:223677] :POSTROUTING ACCEPT [3726:223870] -A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p tcp -m tcp --dport 1723 -j DNAT --to-destination 192.168.1.10 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p gre -j DNAT --to-destination 192.168.1.10 -A PREROUTING -i -h -A POSTROUTING -s 192.168.1.0/24 -o EXT_IF -j MASQUERADE COMMIT # Completed on Thu May 29 12:40:18 2014 # Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *mangle :PREROUTING ACCEPT [22695965:17811993005] :INPUT ACCEPT [13818180:11522330171] :PREROUTING ACCEPT [17865:1053739] :INPUT ACCEPT [5490:357281] :OUTPUT ACCEPT [3723:223677] :POSTROUTING ACCEPT [3726:223870] -A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p tcp -m tcp --dport 1723 -j DNAT --to-destination 192.168.1.10 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p gre -j DNAT --to-destination 192.168.1.10 -A PREROUTING -i -h -A POSTROUTING -s 192.168.1.0/24 -o EXT_IF -j MASQUERADE COMMIT # Completed on Thu May 29 12:40:18 2014 # Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *mangle :PREROUTING ACCEPT [22695965:17811993005] :INPUT ACCEPT [13818180:11522330171] :FORWARD ACCEPT [8527694:6271564562] :OUTPUT ACCEPT [14748508:11899678536] :POSTROUTING ACCEPT [23271280:18170828012] COMMIT # Completed on Thu May 29 12:40:18 2014 hope that I find the solution here ....!! :(

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  • Cisco ASA5505 8.2 Multiple Outside IP to Multiple Inside IP

    - by GriffJ
    Trying to setup ASA5505. Semi working but having issues with accessing services from the outside. ASA5505 Basic License, Version 8.2. (plus upgrade to unlimited inside hosts). Alert: I'm a Cisco Noob. 321.321.39.X is a place holder for privacy. I came up with this config and tested it tonight. ASA Version 8.2(1) ! hostname <removed> domain-name <removed> enable password <removed> encrypted passwd <removed> encrypted names ! interface Vlan1 nameif inside security-level 100 ip address 172.21.36.1 255.255.252.0 ! interface Vlan2 nameif outside security-level 0 ip address 321.321.39.10 255.255.255.248 ! interface Ethernet0/0 switchport access vlan 2 ! interface Ethernet0/1 ! interface Ethernet0/2 ! interface Ethernet0/3 ! interface Ethernet0/4 ! interface Ethernet0/5 ! interface Ethernet0/6 ! interface Ethernet0/7 ! ftp mode passive dns server-group DefaultDNS domain-name <removed> access-list outside_inbound extended permit tcp any host 321.321.39.10 eq pptp access-list outside_inbound extended permit tcp any host 321.321.39.11 eq https access-list outside_inbound extended permit tcp any host 321.321.39.11 eq 993 access-list outside_inbound extended permit tcp any host 321.321.39.11 eq smtp access-list outside_inbound extended permit tcp any host 321.321.39.11 eq 1001 access-list outside_inbound extended permit tcp any host 321.321.39.11 eq 465 access-list outside_inbound extended permit tcp any host 321.321.39.11 eq domain access-list outside_inbound extended permit udp any eq domain host 321.321.39.11 eq domain access-list outside_inbound extended permit tcp any host 321.321.39.12 eq www access-list outside_inbound extended permit tcp any host 321.321.39.12 eq https access-list outside_inbound extended permit tcp any host 321.321.39.13 eq www access-list outside_inbound extended permit tcp any host 321.321.39.13 eq https access-list outside_inbound extended permit icmp any any echo-reply access-list outside_inbound extended permit icmp any any source-quench access-list outside_inbound extended permit icmp any any unreachable access-list outside_inbound extended permit icmp any any time-exceeded access-list outside_inbound extended permit icmp any any traceroute access-list outside_inbound extended permit icmp any any echo pager lines 24 logging asdm informational mtu inside 1500 mtu outside 1500 icmp unreachable rate-limit 1 burst-size 1 no asdm history enable arp timeout 14400 global (outside) 2 321.321.39.11-321.321.39.14 netmask 255.255.255.248 global (outside) 1 interface nat (inside) 1 0.0.0.0 0.0.0.0 static (inside,outside) tcp interface pptp 172.21.37.20 pptp netmask 255.255.255.255 static (inside,outside) 321.321.39.11 172.21.37.14 netmask 255.255.255.255 static (inside,outside) 321.321.39.12 172.21.37.24 netmask 255.255.255.255 static (inside,outside) 321.321.39.13 172.21.37.17 netmask 255.255.255.255 access-group outside_inbound in interface outside route outside 0.0.0.0 0.0.0.0 321.321.39.9 1 route inside 192.168.15.0 255.255.255.0 172.21.36.52 1 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 dynamic-access-policy-record DfltAccessPolicy http server enable http 172.21.36.0 255.255.252.0 inside no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart crypto ipsec security-association lifetime seconds 28800 crypto ipsec security-association lifetime kilobytes 4608000 telnet 172.21.36.0 255.255.252.0 inside telnet timeout 60 ssh timeout 5 console timeout 0 threat-detection basic-threat threat-detection statistics access-list no threat-detection statistics tcp-intercept webvpn ! class-map inspection_default match default-inspection-traffic ! ! policy-map type inspect dns preset_dns_map parameters message-length maximum 512 policy-map global_policy class inspection_default inspect dns preset_dns_map inspect ftp inspect h323 h225 inspect h323 ras inspect rsh inspect rtsp inspect sqlnet inspect skinny inspect sunrpc inspect xdmcp inspect sip inspect netbios inspect tftp inspect pptp inspect ipsec-pass-thru inspect http ! service-policy global_policy global prompt hostname context The servers that had static forwards did not have any outside network access. couldn't ping google.com for instance. mail server couldn't Domain POP the Barracuda spam filter from our ISP etc. So after doing some reading I removed the statics for 172.21.37.11, 12 and 13, and replaced those three with what's below.. static (inside,outside) tcp 321.321.39.11 https 172.21.37.14 https netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.11 993 172.21.37.14 993 netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.11 smtp 172.21.37.14 smtp netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.11 1001 172.21.37.14 1001 netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.11 465 172.21.37.14 465 netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.11 domain 172.21.37.14 domain netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.12 www 172.21.37.24 www netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.12 https 172.21.37.24 https netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.13 www 172.21.37.17 www netmask 255.255.255.255 static (inside,outside) tcp 321.321.39.13 https 172.21.37.17 https netmask 255.255.255.255 Now the servers (for instance 172.21.37.14) could ping the outside world again. Mail started flowing (Domain POP was successful) etc. etc. But I forgot to check if webmail worked from the outside admittedly. But the webservers at 172.21.37.17 and 172.21.37.24 still didn't respond from the outside world. Although I was able to PPTP VPN in on 321.321.39.10 (interface) which is the outside interface IP address. and it is static mapped to 172.21.37.20. So I'm thinking there must be something wrong with NAT somewhere? no response from 321.321.39.11 to 321.321.39.14.. Could anyone look over the config and please let me know what I've done wrong? Is there something I've missed? well obviously but.. please help! Thank you.

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  • Problem with tcp server when converting to service

    - by djerry
    Hello lads, I'm working on monitoring some object (cdr-packets). I'm setting up a tcp-server and am listening on port 50043 for the packages. The program as a console application is working just fine, my server is working like it should and i'm receiving the packets. When i try to use it as a service, i cannot seem to get a client connected to my server. Is there something i need to change to deploy this as a service? Code below is from my application: this is my service class where i start protected override void OnStart(string[] args) { server = new TcpServer(); server.StartServer(); } this is the constructor of TcpServer public TcpServer() { try { _server = new TcpListener(IPAddress.Any, 50043); } catch (Exception) { _server = null; } } this is the method i call after initialising the class public void StartServer() { if (_server != null) { // Create a ArrayList for storing SocketListeners before starting the server. _socketListenersList = new ArrayList(); // Start the Server and start the thread to listen client requests. _server.Start(); _serverThread = new Thread(new ThreadStart(ServerThreadStart)); _serverThread.Start(); // Create a low priority thread that checks and deletes client // SocktConnection objcts that are marked for deletion. _purgingThread = new Thread(new ThreadStart(PurgingThreadStart)); _purgingThread.Priority = ThreadPriority.Lowest; _purgingThread.Start(); } } this is the thread that keep checking if any client tries to connect private void ServerThreadStart() { // Client Socket variable; Socket clientSocket = null; TcpSocketListener socketListener = null; while (!_stopServer) { try { // Wait for any client requests and if there is any request from any //client accept it (Wait indefinitely). clientSocket = _server.AcceptSocket(); // Create a SocketListener object for the client. socketListener = new TcpSocketListener(clientSocket); // Add the socket listener to an array list in a thread safe fashon. lock (_socketListenersList) { _socketListenersList.Add(socketListener); } // Start a communicating with the client in a different thread. socketListener.StartSocketListener(); } catch (SocketException se) { _stopServer = true; } } } when for the first time a packet waits to be read, and i get to "clientSocket = _server.AcceptSocket();", it throws an exception (service, not very good debugable) Does anyone recognize this problem or can help me? Thanks in advance

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  • Abnormally disconnected TCP sockets and write timeout

    - by James
    Hello I will try to explain the problem in shortest possible words. I am using c++ builder 2010. I am using TIdTCPServer and sending voice packets to a list of connected clients. Everything works ok untill any client is disconnected abnormally, For example power failure etc. I can reproduce similar disconnect by cutting the ethernet connection of a connected client. So now we have a disconnected socket but as you know it is not yet detected at server side so server will continue to try to send data to that client too. But when server try to write data to that disconnected client ...... Write() or WriteLn() HANGS there in trying to write, It is like it is wating for somekind of Write timeout. This hangs the hole packet distribution process as a result creating a lag in data transmission to all other clients. After few seconds "Socket Connection Closed" Exception is raised and data flow continues. Here is the code try { EnterCriticalSection(&SlotListenersCriticalSection); for(int i=0;i<SlotListeners->Count;i++) { try { //Here the process will HANG for several seconds on a disconnected socket ((TIdContext*) SlotListeners->Objects[i])->Connection->IOHandler->WriteLn("Some DATA"); }catch(Exception &e) { SlotListeners->Delete(i); } } }__finally { LeaveCriticalSection(&SlotListenersCriticalSection); } Ok i already have a keep alive mechanism which disconnect the socket after n seconds of inactivity. But as you can imagine, still this mechnism cant sync exactly with this braodcasting loop because this braodcasting loop is running almost all the time. So is there any Write timeouts i can specify may be through iohandler or something ? I have seen many many threads about "Detecting disconnected tcp socket" but my problem is little different, i need to avoid that hangup for few seconds during the write attempt. So is there any solution ? Or should i consider using some different mechanism for such data broadcasting for example the broadcasting loop put the data packet in some kind of FIFO buffer and client threads continuously check for available data and pick and deliver it to themselves ? This way if one thread hangs it will not stop/delay the over all distribution thread. Any ideas please ? Thanks for your time and help. Regards Jams

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  • probelm with recv() on a tcp connection

    - by michael
    Hi, I am simulating TCP communication on windows in C I have sender and a receiver communicating. sender sends packets of specific size to receiver. receiver gets them and send an ACK for each packet it received back to the sender. If the sender didn't get a specific packet (they are numbered in a header inside the packet) it sends the packet again to the receiver. Here is the getPacket function on the receiver side: //get the next packet from the socket. set the packetSize to -1 //if it's the first packet. //return: total bytes read // return: 0 if socket has shutdown on sender side, -1 error, else number of bytes received int getPakcet(char *chunkBuff,int packetSize,SOCKET AcceptSocket){ int totalChunkLen = 0; int bytesRecv=-1; bool firstTime=false; if (packetSize==-1) { packetSize=MAX_PACKET_LENGTH; firstTime=true; } int needToGet=packetSize; do { char* recvBuff; recvBuff = (char*)calloc(needToGet,sizeof(char)); if(recvBuff == NULL){ fprintf(stderr,"Memory allocation problem\n"); return -1; } bytesRecv = recv(AcceptSocket, recvBuff, needToGet, 0); if (bytesRecv == SOCKET_ERROR){ fprintf(stderr,"recv() error %ld.\n", WSAGetLastError()); totalChunkLen=-1; return -1; } if (bytesRecv == 0){ fprintf(stderr,"recv(): socket has shutdown on sender side"); return 0; } else if(bytesRecv > 0) { memcpy(chunkBuff + totalChunkLen,recvBuff,bytesRecv); totalChunkLen+=bytesRecv; } needToGet-=bytesRecv; } while ((totalChunkLen < packetSize) && (!firstTime)); return totalChunkLen; } i use firstTime because for the first time the receiver doesn't know the normal package size that the sender is going to send to it, so i use a MAX_PACKET_LENGTH to get a package and then set the normal package size to the num of bytes i have received my problem is the last package. it's size is less than the package size so lets say last package size is 2 and the normal package size is 4. so recv() gets two bytes, continues to the while condition, then totalChunkLen < packetSize because 2<4 so it iterates the loop again and the gets stuck in recv() because it's blocking because the sender has nothing to send. on the sender side i can't close the connection because i didn't ACK back, so it's kind of a deadlock. receiver is stuck because it's waiting for more packages but sender has nothing to send. i don't want to use a timeout for recv() or to insert a special character to the package header to mark that it is the last one what can i do ? thanks

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  • how to create multiple tcp connections between server and client

    - by lowcosthighperformance
    I am new in Unix/Linux networking programming, so I have written server-client program in below.In this code there is one socket between client and server, client requests to server, then server responses from 1 to 100 numbers to client. So my question is how can we do this process with 3 socket( tcp connection) without using thread? ( e.g. First socket runs then second runs then third runs then first again .. ) Do you have any suggestion? Thank you client.c int main() { int sock; struct sockaddr_in sa; int ret; char buf[1024]; int x; sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_port = htons(SERVER_PORT); inet_pton (AF_INET, SERVER_IP, &sa.sin_addr); ret = connect (sock, (const struct sockaddr *) &sa,sizeof (sa)); if (ret != 0) { printf ("connect failed\n"); exit (0); } x = 0; while (x != -1) { read (sock, buf , sizeof(int)); x = ntohl(*((int *)buf)); if (x != -1) printf ("int rcvd = %d\n", x); } close (sock); exit (0); } server.c int main() { int list_sock; int conn_sock; struct sockaddr_in sa, ca; socklen_t ca_len; char buf[1024]; int i; char ipaddrstr[IPSTRLEN]; list_sock = socket (AF_INET, SOCK_STREAM, 0); bzero (&sa, sizeof(sa)); sa.sin_family = AF_INET; sa.sin_addr.s_addr = htonl(INADDR_ANY); sa.sin_port = htons(SERVER_PORT); bind (list_sock,(struct sockaddr *) &sa,sizeof(sa)); listen (list_sock, 5); while (1){ bzero (&ca, sizeof(ca)); ca_len = sizeof(ca); // important to initialize conn_sock = accept (list_sock,(struct sockaddr *) &ca,&ca_len); printf ("connection from: ip=%s port=%d \n",inet_ntop(AF_INET, &(ca.sin_addr), ipaddrstr, IPSTRLEN),ntohs(ca.sin_port)); for (i=0; i<100; ++i){ *((int *)buf) = htonl(i+20); // we using converting to network byte order write (conn_sock, buf, sizeof(int)); } * ((int *)buf) = htonl(-1); write (conn_sock, buf, sizeof(int)); close (conn_sock); printf ("server closed connection to client\n"); } }

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