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  • Data Access Layer, Best Practices

    - by labratmatt
    I'm looking for input on the best way to refactor the data access layer (DAL) in my PHP based web app. I follow an MVC pattern: PHP/HTML/CSS/etc. views on the front end, PHP controllers/services in the middle, and a PHP DAL sitting on top of a relational database in the model. Pretty standard stuff. Things are working fine, but my DAL is getting large (codesmell?) and becoming a bit unwieldy. My DAL contains almost all of the logic to interface with my database and is full of functions that look like this: function getUser($user_id) { $statement = "select id, name from users where user_id=:user_id"; PDO builds statement and fetchs results as an array return $array_of_results_generated_by_PDO_fetch_method; } Notes: The logic in my controller only interacts with the model using functions like the above in the DAL I am not using a framework (I'm of the opinion that PHP is a templating language and there's no need to inject complexity via a framework) I generally use PHP as a procedural language and tend to shy away from its OOP approach (I enjoy OOP development but prefer to keep that complexity out of PHP) What approaches have you taken when your DAL has reached this point? Do I have a fundamental design problem? Do I simply need to chop my DAL into a number of smaller files (logically divide it)? Thanks.

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  • Java NIO SocketChannel writing problem

    - by Nilesh
    I am using Java NIO's SocketChannel to write : int n = socketChannel.write(byteBuffer); Most of the times the data is sent in one or two parts; i.e. if the data could not be sent in one attemmpt, remaining data is retried. The issue here is, sometimes, the data is not being sent completely in one attempt, rest of the data when tried to send multiple times, it occurs that even after trying several times, not a single character is being written to channel, finally after some time the remaning data is sent. What could be the cause of such behaviour? Could external factors such as RAM, etc cause the hindarance? Please help me solve this issue. If any other information is required please let me know. Thanks

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  • What is the best folder stucture in TFS for reporting service projects

    - by Dave
    Hi, I'm looking for some help on deciding a useful folder stucture strategy for reporting service projects in TFS. Does any one have some suggestions on which way I should stucture TFS? Should it be a project per report or should it be one Reporting project with multiple folders under the main that contain all the report projects? i.e. Senario 1 (separate projects for each report project) $ReportProject1 $ReportProject2 $ReportProject3 Senario 2 (Main report project in TFS and subfolders with report projects) $ReportingServices ------Src ---------Project1 -----------ReportProject1 files ---------Project2 -----------ReportProject2 files ---------Project3 -----------ReportProject3 files

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  • Multiple Socket Connections

    - by BSchlinker
    I need to write a server which accepts connections from multiple client machines, maintains track of connected clients and sends individual clients data as necessary. Sometimes, all clients may be contacted at once with the same message, other times, it may be one individual client or a group of clients. Since I need confirmation that the clients received the information and don't want to build an ACK structure for a UDP connection, I decided to use a TCP streaming method. However, I've been struggling to understand how to maintain multiple connections and keep them idle. I seem to have three options. Use a fork for each incoming connection to create a separate child process, use pthread_create to create an entire new thread for each process, or use select() to wait on all open socket IDs for a connection. Recommendations as to how to attack this? I've begun working with pthreads but since performance will likely not be an issue, multicore processing is not necessary and perhaps there is a simpler way.

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  • Entropy using Decision Tree's

    - by Matt Clements
    Train a decision tree on the data represented by attributes A1, A2, A3 and outcome C described below: A1 A2 A3 C 1 0 1 0 0 1 1 1 0 0 1 0 For log2(1/3) = 1.6 and log2(2/3) = 0.6, answer the following questions: a) What is the value of entropy H for the given set of training example? b) What is the portion of the positive samples split by attribute A2? c) What is the value of information gain, G(A2), of attribute A2? d) What is IFTHEN rule(s) for the decision tree?

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  • What is the right approach to checksumming UDP packets

    - by mr.b
    I'm building UDP server application in C#. I've come across a packet checksum problem. As you probably know, each packet should carry some simple way of telling receiver if packet data is intact. Now, UDP already has 2-byte checksum as part of header, which is optional, at least in IPv4 world. Alternative method is to have custom checksum as part of data section in each packet, and to verify it on receiver. My question boils down to: is it better to rely on (optional) checksum in UDP packet header, or to make a custom checksum implementation as part of packet data section? Perhaps the right answer depends on circumstances (as usual), so one circumstance here is that, even though code is written and developed in .NET on Windows, it might have to run under platform-independent Mono.NET, so eventual solution should be compatible with other platforms. I believe that custom checksum algorithm would be easily portable, but I'm not so sure about the first one. Any thoughts? Also, shouts about packet checksumming in general are welcome.

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  • Erlang OTP application design

    - by Toby Hede
    I am struggling a little coming to grips with the OTP development model as I convert some code into an OTP app. I am essentially making a web crawler and I just don't quite know where to put the code that does the actual work. I have a supervisor which starts my worker: -behaviour(supervisor). -define(CHILD(I, Type), {I, {I, start_link, []}, permanent, 5000, Type, [I]}). init(_Args) -> Children = [ ?CHILD(crawler, worker) ], RestartStrategy = {one_for_one, 0, 1}, {ok, {RestartStrategy, Children}}. In this design, the Crawler Worker is then responsible for doing the actual work: -behaviour(gen_server). start_link() -> gen_server:start_link(?MODULE, [], []). init([]) -> inets:start(), httpc:set_options([{verbose_mode,true}]), % gen_server:cast(?MODULE, crawl), % ok = do_crawl(), {ok, #state{}}. do_crawl() -> % crawl! ok. handle_cast(crawl}, State) -> ok = do_crawl(), {noreply, State}; do_crawl spawns a fairly large number of processes and requests that handle the work of crawling via http. Question, ultimately is: where should the actual crawl happen? As can be seen above I have been experimenting with different ways of triggering the actual work, but still missing some concept essential for grokering the way things fit together. Note: some of the OTP plumbing is left out for brevity - the plumbing is all there and the system all hangs together

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  • Architectural conundrum

    - by Dejan
    The worst thing when working on a one man project is the lack of input that you usually get from your coworkers. And because of the lack of that you tend to make obvious mistakes. After going down that road for some time I would need some help from the community. I started a little home-brew project that should turn into a portal of some sorts. And the main thing that is bothering me is the persistence layer that i have concocted. It should be completely separated from the presentation layer for starters and a OR mapper is also somewhere. This is because I have multiple data stores that have to be used. So the base idea was that the individual "repositories" operate each on their individual database and that the business layer then aggregates the business objects which are then transformed in the presentation layer into view objects. The main problem I face is the following: Multiple classes for the same concept - There is a DAL representation of a user and BL representation of user and a view representation of a user. I can handle the transformation with a tool but is this really the right way. I mean they are all nicely separated, but the overhead is quite something. What do you think? Am I going too deep into the separation of concern rabbit hole or is this still normal?

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  • Reinforcement learning And POMDP

    - by Betamoo
    I am trying to use Multi-Layer NN to implement probability function in Partially Observable Markov Process.. I thought inputs to the NN would be: current state, selected action, result state; The output is a probability in [0,1] (prob. that performing selected action on current state will lead to result state) In training, I fed the inputs stated before, into the NN, and I taught it the output=1.0 for each case that already occurred. The problem : For nearly all test case the output probability is near 0.95.. no output was under 0.9 ! Even for nearly impossible results, it gave that high prob. PS:I think this is because I taught it happened cases only, but not un-happened ones.. But I can not at each step in the episode teach it the output=0.0 for every un-happened action! Any suggestions how to over come this problem? Or may be another way to use NN or to implement prob function? Thanks

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  • How to structure an enterprise MVC app, and where does Business Logic go?

    - by James
    I am an MVC newbie. As far as I can tell: Controller: deals with routing requests View: deals with presentation of data Model: looks a whole lot like a Data Access layer Where does the Business Logic go? Take a large enterprise application with: Several different sources of data (WCF, WebServices and ADO) tied together in a data access layer (useing multiple different DTOs). A lot business logic segmented over several dlls. What is an appropriate way for an MVC web application to sit on top of this (in terms of code and project structure)? The example I have seen where everything just goes in the Model folder don't seem like they are appropriate for very large applications. Thanks for any advice!

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  • C#: Inheritance, Overriding, and Hiding

    - by Rosarch
    I'm having difficulty with an architectural decision for my C# XNA game. The basic entity in the world, such as a tree, zombie, or the player, is represented as a GameObject. Each GameObject is composed of at least a GameObjectController, GameObjectModel, and GameObjectView. These three are enough for simple entities, like inanimate trees or rocks. However, as I try to keep the functionality as factored out as possible, the inheritance begins to feel unwieldy. Syntactically, I'm not even sure how best to accomplish my goals. Here is the GameObjectController: public class GameObjectController { protected GameObjectModel model; protected GameObjectView view; public GameObjectController(GameObjectManager gameObjectManager) { this.gameObjectManager = gameObjectManager; model = new GameObjectModel(this); view = new GameObjectView(this); } public GameObjectManager GameObjectManager { get { return gameObjectManager; } } public virtual GameObjectView View { get { return view; } } public virtual GameObjectModel Model { get { return model; } } public virtual void Update(long tick) { } } I want to specify that each subclass of GameObjectController will have accessible at least a GameObjectView and GameObjectModel. If subclasses are fine using those classes, but perhaps are overriding for a more sophisticated Update() method, I don't want them to have to duplicate the code to produce those dependencies. So, the GameObjectController constructor sets those objects up. However, some objects do want to override the model and view. This is where the trouble comes in. Some objects need to fight, so they are CombatantGameObjects: public class CombatantGameObject : GameObjectController { protected new readonly CombatantGameModel model; public new virtual CombatantGameModel Model { get { return model; } } protected readonly CombatEngine combatEngine; public CombatantGameObject(GameObjectManager gameObjectManager, CombatEngine combatEngine) : base(gameObjectManager) { model = new CombatantGameModel(this); this.combatEngine = combatEngine; } public override void Update(long tick) { if (model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); } base.Update(tick); } } Still pretty simple. Is my use of new to hide instance variables correct? Note that I'm assigning CombatantObjectController.model here, even though GameObjectController.Model was already set. And, combatants don't need any special view functionality, so they leave GameObjectController.View alone. Then I get down to the PlayerController, at which a bug is found. public class PlayerController : CombatantGameObject { private readonly IInputReader inputReader; private new readonly PlayerModel model; public new PlayerModel Model { get { return model; } } private float lastInventoryIndexAt; private float lastThrowAt; public PlayerController(GameObjectManager gameObjectManager, IInputReader inputReader, CombatEngine combatEngine) : base(gameObjectManager, combatEngine) { this.inputReader = inputReader; model = new PlayerModel(this); Model.Health = Constants.PLAYER_HEALTH; } public override void Update(long tick) { if (Model.Health <= 0) { gameObjectManager.RemoveFromWorld(this); for (int i = 0; i < 10; i++) { Debug.WriteLine("YOU DEAD SON!!!"); } return; } UpdateFromInput(tick); // .... } } The first time that this line is executed, I get a null reference exception: model.Body.ApplyImpulse(movementImpulse, model.Position); model.Position looks at model.Body, which is null. This is a function that initializes GameObjects before they are deployed into the world: public void Initialize(GameObjectController controller, IDictionary<string, string> data, WorldState worldState) { controller.View.read(data); controller.View.createSpriteAnimations(data, _assets); controller.Model.read(data); SetUpPhysics(controller, worldState, controller.Model.BoundingCircleRadius, Single.Parse(data["x"]), Single.Parse(data["y"]), bool.Parse(data["isBullet"])); } Every object is passed as a GameObjectController. Does that mean that if the object is really a PlayerController, controller.Model will refer to the base's GameObjectModel and not the PlayerController's overriden PlayerObjectModel? In response to rh: This means that now for a PlayerModel p, p.Model is not equivalent to ((CombatantGameObject)p).Model, and also not equivalent to ((GameObjectController)p).Model. That is exactly what I do not want. I want: PlayerController p; p.Model == ((CombatantGameObject)p).Model p.Model == ((GameObjectController)p).Model How can I do this? override?

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  • When should I use Dependency Injection and when utility methods?

    - by Roman
    I have a Java EE project with Spring IoC container. I've just found in Utils class static method sendMail(long list of params). I don't know why but I feel that it would look better if we had separate class (Spring bean with singleton scope) which will be responsible for sending email. But I can't find any arguments which can prove my position. So, are there any pros (or cons) in using DI in this (rather general) situation?

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  • Odd performance with C# Asynchronous server socket

    - by The.Anti.9
    I'm working on a web server in C# and I have it running on Asynchronous socket calls. The weird thing is that for some reason, when you start loading pages, the 3rd request is where the browser won't connect. It just keeps saying "Connecting..." and doesn't ever stop. If I hit stop. and then refresh, it will load again, but if I try another time after that it does the thing where it doesn't load again. And it continues in that cycle. I'm not really sure what is making it do that. The code is kind of hacked together from a couple of examples and some old code I had. Any miscellaneous tips would be helpful as well. Heres my little Listener class that handles everything (pastied here. thought it might be easier to read this way) using System; using System.Collections.Generic; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; namespace irek.Server { public class Listener { private int port; private Socket server; private Byte[] data = new Byte[2048]; static ManualResetEvent allDone = new ManualResetEvent(false); public Listener(int _port) { port = _port; } public void Run() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, port); server.Bind(iep); Console.WriteLine("Server Initialized."); server.Listen(5); Console.WriteLine("Listening..."); while (true) { allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); allDone.WaitOne(); } } private void AcceptCon(IAsyncResult iar) { allDone.Set(); Socket s = (Socket)iar.AsyncState; Socket s2 = s.EndAccept(iar); SocketStateObject state = new SocketStateObject(); state.workSocket = s2; s2.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); } private void Read(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; Socket s = state.workSocket; int read = s.EndReceive(iar); if (read > 0) { state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, read)); if (s.Available > 0) { s.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); return; } } if (state.sb.Length > 1) { string requestString = state.sb.ToString(); // HANDLE REQUEST HERE // Temporary response string resp = "<h1>It Works!</h1>"; string head = "HTTP/1.1 200 OK\r\nContent-Type: text/html;\r\nServer: irek\r\nContent-Length:"+resp.Length+"\r\n\r\n"; byte[] answer = Encoding.ASCII.GetBytes(head+resp); // end temp. state.workSocket.BeginSend(answer, 0, answer.Length, SocketFlags.None, new AsyncCallback(Send), state.workSocket); } } catch (Exception) { return; } } private void Send(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; int sent = state.workSocket.EndSend(iar); state.workSocket.Shutdown(SocketShutdown.Both); state.workSocket.Close(); } catch (Exception) { } return; } } } And my SocketStateObject: public class SocketStateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); }

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  • VS 2010 Layer Diagram Validation Error is Showing A Dependency That Doesn't Even Exist (AV0001)

    - by Dan
    I'm getting the following validation error on my layer diagram Error 65 AV0001 : Invalid Dependency : Weld.Interface.Core(Assembly) -- Weld.Interface(Namespace) Layers: Application Framework Core, Application Framework | Dependencies: Namespace Reference D:\Projects\Windows Projects\Weld\Weld\ModelingProject1\Weld.layerdiagram 0 0 ModelingProject1 Weld.Interface.Core: This assembly and namespace does not have a reference to Weld.Interface and only references .NET Framework classes Weld.Interface: This assembly and namespace does not have a reference to Weld.Interface There is no dependancy between these two layers in the dependency diagram. I am confused why I am getting this error. No dependency in the project or code, and no dependency is even setup in the layer diagram. Somehow the Validation logic in the layer diagram is seeing a non existant dependency and saying it is an error. Any ideas what either I might have missed or what is causing this problem?

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  • Squid handling of concurrent cache misses

    - by Oliver H-H
    We're using a Squid cache to off-load traffic from our web servers, ie. it's setup as a reverse-proxy responding to inbound requests before they hit our web servers. When we get blitzed with concurrent requests for the same request that's not in the cache, Squid proxies all the requests through to our web ("origin") servers. For us, this behavior isn't ideal: our origin servers gets bogged down trying to fulfill N identical requests concurrently. Instead, we'd like the first request to proxy through to the origin server, the rest of the requests to queue at the Squid layer, and then all be fulfilled by Squid when the origin server has responded to that first request. Does anyone know how to configure Squid to do this? We've read through the documentation multiple times and thoroughly web-searched the topic, but can't figure out how to do it. We use Akamai too and, interestingly, this is its default behavior. (However, Akamai has so many nodes that we still see lots of concurrent requests in certain traffic spike scenarios, even with Akamai's super-node feature enabled.) This behavior is clearly configurable for some other caches, eg. the Ehcache documentation offers the option "Concurrent Cache Misses: A cache miss will cause the filter chain, upstream of the caching filter to be processed. To avoid threads requesting the same key to do useless duplicate work, these threads block behind the first thread." Some folks call this behavior a "blocking cache," since the subsequent concurrent requests block behind the first request until it's fulfilled or timed-out. Thx for looking over my noob question! Oliver

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  • How to File Transfer client to Server?

    - by Phsika
    i try to recieve a file from server but give me error on server.Start() ERROR : In a manner not permitted by the access permissions to access a socket was attempted to How can i solve it? private void btn_Recieve_Click(object sender, EventArgs e) { TcpListener server = null; // Set the TcpListener on port 13000. Int32 port = 13000; IPAddress localAddr = IPAddress.Parse("192.168.1.201"); // TcpListener server = new TcpListener(port); server = new TcpListener(localAddr, port); // Start listening for client requests. server.Start(); // Buffer for reading data Byte[] bytes = new Byte[277577]; String data; data = null; // Perform a blocking call to accept requests. // You could also user server.AcceptSocket() here. TcpClient client = server.AcceptTcpClient(); NetworkStream stream = client.GetStream(); int i; i = stream.Read(bytes, 0, 277577); BinaryWriter writer = new BinaryWriter(File.Open("GoodLuckToMe.jpg", FileMode.Create)); writer.Write(bytes); writer.Close(); client.Close(); }

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  • How to choose programming language for projects?

    - by bdhar
    This is a question I constantly encounter when I attend any technical forums / discussions / interviews. There is a similar article but it focuses on business merits as well. What I am looking for is a guide (not a checklist like this one which is abstract and not so accurate) which helps an architect to choose the programming language to implement a requirement. Is there a book or article available for the same purpose?

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  • How to avoid injecting dependencies into an object so that it can pass them on?

    - by Pheter
    I am interested in applying dependency injection to my current project, which makes use of the MVC pattern. My controllers will call the models and therefore will need to inject the dependencies into the models. To do this, the controller must have the dependencies (such as a database object) in the first place. The controller doesn't need to make use of some of these dependencies (such as the database object), so I feel that it shouldn't be given this dependency. However, it has to have these dependencies if it is to inject them into the model objects. How can I avoid having dependencies injected into an object just so that it can pass them on? Doing so feels wrong and can result in many dependencies being injected into an object. Edit: I am using PHP.

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  • Rewriting Live TCP Streams

    - by user213060
    I want to rewrite TCP/IP streams. Ettercap's etterfilter command lets you perform simple live replacements of TCP/IP data based on fixed strings or regexes. Example: http://ettercap.sourceforge.net/forum/viewtopic.php?t=2833 I would like to rewrite streams based on my own filter program instead of just simple string replacements. Anyone have an idea of how to do this? Is there anything other than Ettercap that can do live replacement like this, maybe as a plugin to a VPN software or something? Thanks!

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  • packet mmap send packet format

    - by SeregASM
    I want to improve packet transmitting performance. Before that I used raw sockets and now I study packet_mmap. I have packets(frames) which I already captured from kernel module from another PC, put to current PC and now I want to retransmit them to local interface with following forwarding. I have got example of packet_mmap, integrated it to my project, but I send fd_socket = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); memset(&my_addr, 0, sizeof(struct sockaddr_ll)); my_addr.sll_family = PF_PACKET; my_addr.sll_protocol = htons(ETH_P_ALL); strcpy(str_devname, "eth0"); strncpy(s_ifr.ifr_name, str_devname, sizeof(s_ifr.ifr_name)); ec = ioctl(fd_socket, SIOCGIFINDEX, &s_ifr); i_ifindex = s_ifr.ifr_ifindex; memset(&my_addr, 0, sizeof(struct sockaddr_ll)); my_addr.sll_family = AF_PACKET; my_addr.sll_protocol = ETH_P_ALL; my_addr.sll_ifindex = i_ifindex; bind(fd_socket, (struct sockaddr *) &my_addr, sizeof(struct sockaddr_ll) s_packet_req.tp_block_size = c_buffer_sz; s_packet_req.tp_frame_size = c_buffer_sz; s_packet_req.tp_block_nr = c_buffer_nb; s_packet_req.tp_frame_nr = c_buffer_nb; size = s_packet_req.tp_block_size * s_packet_req.tp_block_nr; if (setsockopt(fd_socket, SOL_PACKET, PACKET_TX_RING, (char *) &s_packet_req, sizeof(s_packet_req)) < 0) { perror("setsockopt: PACKET_TX_RING"); return; } if (c_sndbuf_sz) { printf("send buff size = %d\n", c_sndbuf_sz); if (setsockopt(fd_socket, SOL_SOCKET, SO_SNDBUF, &c_sndbuf_sz, sizeof(c_sndbuf_sz)) < 0){ perror("getsockopt: SO_SNDBUF"); exit(1); } } data_offset = TPACKET_HDRLEN - sizeof(struct sockaddr_ll); printf("data offset = %d bytes\n", data_offset); ps_header_start = (tpacket_hdr *) mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd_socket, 0); if (ps_header_start == (void*) -1) { perror("mmap"); exit(1); } Then I fill data ps_header = ((struct tpacket_hdr *) ((char *) ps_header_start + (c_buffer_sz * i_index))); if (!ps_header) { perror("ps_header") ; return NULL; } data = ((char*) ps_header) + data_offset; switch ((volatile uint32_t) ps_header->tp_status) { case TP_STATUS_AVAILABLE: printf("TP_STATUS_AVAILABLE, index=%d\n",i_index) ; memcpy(data, packet_data, size); pthread_mutex_lock(&index_locker) ; i_index++; pthread_mutex_unlock(&index_locker) ; if (i_index >= c_buffer_nb) { i_index = 0; first_loop = 0; } /* update packet len */ ps_header->tp_len = size; /* set header flag to USER (trigs xmit)*/ ps_header->tp_status = TP_STATUS_SEND_REQUEST; then I send ec_send = sendto(fd_socket, NULL, 0, 0, (struct sockaddr *) ps_sockaddr, sizeof(struct sockaddr_ll)); I have got no errors, ec_send=not null size of sended data. But there are no data routed to destination host. So, I ask - what data I should pass to ring buffer, now I include headers ip,tcp, should I include MAC header? - May be I have to set additional flags to route my packets.

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