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  • Where do I handle asynchronous exceptions?

    - by Jurily
    Consider the following code: class Foo { // boring parts omitted private TcpClient socket; public void Connect(){ socket.BeginConnect(Host, Port, new AsyncCallback(cbConnect), quux); } private void cbConnect(IAsyncResult result){ // blah } } If socket throws an exception after BeginConnect returns and before cbConnect gets called, where does it pop up? Is it even allowed to throw in the background?

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  • some OVERLAPS using WSASend not returning in a timely manner using GetQueuedCompletionStatus?

    - by Geoffrey
    Background: I'm using CreateIoCompletionPort, WSASend/Recv, and GetQueuedCompletionStatus to do overlapped socket io on my server. For flow control, when sending to the client, I only allow several WSASend() to be called when all pending OVERLAPs have popped off the IOCP. Problem: Recently, there are occassions when the OVERLAPs do not get returned to the IOCP. The thread calling GetQueuedCompletionStatus does not get them and they remain in my local pending queue. I've verified that the client DOES receive the data off the socket and the socket is connected. No errors were returned when the WSASend() calls were made. The OVERLAPs simply "never" come back without an external stimulus like the following: Disconnecting the socket from the client or server, immediately allows the GetQueuedCompletionStatus thread to retrieve the OVERLAPs Making additional calls to WSASend(), sometimes several are needed, before all the OVERLAPs suddenly pop off the queue. Question: Has anyone seen this type of behavior? Any ideas on what is causing this? Thanks, Geoffrey

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  • Problem while adding a new value to a hashtable when it is enumerated

    - by karthik
    `hi I am doing a simple synchronous socket programming,in which i employed twothreads one for accepting the client and put the socket object into a collection,other thread will loop through the collection and send message to each client through the socket object. the problem is 1.i connect to clients to the server and start send messages 2.now i want to connect a new client,while doing this i cant update the collection and add a new client to my hashtable.it raises an exception "collection modified .Enumeration operation may not execute" how to add a NEW value without having problems in a hashtable. private void Listen() { try { //lblStatus.Text = "Server Started Listening"; while (true) { Socket ReceiveSock = ServerSock.Accept(); //keys.Clear(); ConnectedClients = new ListViewItem(); ConnectedClients.Text = ReceiveSock.RemoteEndPoint.ToString(); ConnectedClients.SubItems.Add("Connected"); ConnectedList.Items.Add(ConnectedClients); ClientTable.Add(ReceiveSock.RemoteEndPoint.ToString(), ReceiveSock); //foreach (System.Collections.DictionaryEntry de in ClientTable) //{ // keys.Add(de.Key.ToString()); //} //ClientTab.Add( //keys.Add( } //lblStatus.Text = "Client Connected Successfully."; } catch (Exception ex) { MessageBox.Show(ex.Message); } } private void btn_receive_Click(object sender, EventArgs e) { Thread receiveThread = new Thread(new ThreadStart(Receive)); receiveThread.IsBackground = true; receiveThread.Start(); } private void Receive() { while (true) { //lblMsg.Text = ""; byte[] Byt = new byte[2048]; //ReceiveSock.Receive(Byt); lblMsg.Text = Encoding.ASCII.GetString(Byt); } } private void btn_Send_Click(object sender, EventArgs e) { Thread SendThread = new Thread(new ThreadStart(SendMsg)); SendThread.IsBackground = true; SendThread.Start(); } private void btnlist_Click(object sender, EventArgs e) { //Thread ListThread = new Thread(new ThreadStart(Configure)); //ListThread.IsBackground = true; //ListThread.Start(); } private void SendMsg() { while (true) { try { foreach (object SockObj in ClientTable.Keys) { byte[] Tosend = new byte[2048]; Socket s = (Socket)ClientTable[SockObj]; Tosend = Encoding.ASCII.GetBytes("FirstValue&" + GenerateRandom.Next(6, 10).ToString()); s.Send(Tosend); //ReceiveSock.Send(Tosend); Thread.Sleep(300); } } catch (Exception ex) { MessageBox.Show(ex.Message); } } }

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  • getting global name not defined error

    - by nashr rafeeg
    i have the following class class notify(): def __init__(self,server="localhost", port=23053): self.host = server self.port = port register = gntp.GNTPRegister() register.add_header('Application-Name',"SVN Monitor") register.add_notification("svnupdate",True) growl(register) def svn_update(self, author="Unknown", files=0): notice = gntp.GNTPNotice() notice.add_header('Application-Name',"SVN Monitor") notice.add_header('Notification-Name', "svnupdate") notice.add_header('Notification-Title',"SVN Commit") # notice.add_header('Notification-Icon',"") notice.add_header('Notification-Text',Msg) growl(notice) def growl(data): s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((self.host,self.port)) s.send(data) response = gntp.parse_gntp(s.recv(1024)) print response s.close() but when ever i try to use this class via the follwoing code i get 'NameError: global name 'growl' is not defined' from growlnotify import * n = notify() n.svn_update() any one has an idea what is going on here ? cheers nash

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  • accessing required modules from other modules

    - by john smith
    I have a bare-bone express application, exactly the one that is created with the express command. I have installed socket.io and attached it to my server, like this: var app = express(), server = http.createServer(app), io = io.listen(server); server.listen(8000); Now, I also have the routes files, which is called like this: app.get('/', routes.index); Inside this module I have the following function: exports.index = function(req, res){ socket.emit('news', { message: "foo" }); }; This obviously leads to a 500 reference error, because the routes file is an exportable module, and obviously has no idea what the socket is, as it is located in the app.js file. Is there a way I can access this socket object from this, or any other file? Please note that it is attached to the express generated app. extra: what about getting/setting session data? Thanks in advance.

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  • c windows connect() fails. error 10049

    - by Joshua Moore
    The following two pieces of code compile, but I get a connect() failed error on the client side. (compiled with MinGW). Client Code: // thanks to cs.baylor.edu/~donahoo/practical/CSockets/code/TCPEchoClientWS.c #include <stdio.h> #include <winsock.h> #include <stdlib.h> #define RCVBUFSIZE 32 // size of receive buffer void DieWithError(char *errorMessage); int main(int argc, char* argv[]) { int sock; struct sockaddr_in echoServAddr; unsigned short echoServPort; char *servIP; char *echoString; char echoBuffer[RCVBUFSIZE]; int echoStringLen; int bytesRcvd, totalBytesRcvd; WSAData wsaData; if((argc < 3) || (argc > 4)){ fprintf(stderr, "Usage: %s <Sever IP> <Echo Word> [<Echo Port>]\n", argv[0]); exit(1); } if (argc==4) echoServPort = atoi(argv[3]); // use given port if any else echoServPort = 7; // echo is well-known port for echo service if(WSAStartup(MAKEWORD(2, 0), &wsaData) != 0){ // load winsock 2.0 dll fprintf(stderr, "WSAStartup() failed"); exit(1); } // create reliable, stream socket using tcp if((sock=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) DieWithError("socket() failed"); // construct the server address structure memset(&echoServAddr, 0, sizeof(echoServAddr)); echoServAddr.sin_family = AF_INET; echoServAddr.sin_addr.s_addr = inet_addr(servIP); // server IP address echoServAddr.sin_port = htons(echoServPort); // establish connection to the echo server if(connect(sock, (struct sockaddr*)&echoServAddr, sizeof(echoServAddr)) < 0) DieWithError("connect() failed"); echoStringLen = strlen(echoString); // determine input length // send the string, includeing the null terminator to the server if(send(sock, echoString, echoStringLen, 0)!= echoStringLen) DieWithError("send() sent a different number of bytes than expected"); totalBytesRcvd = 0; printf("Received: "); // setup to print the echoed string while(totalBytesRcvd < echoStringLen){ // receive up to the buffer size (minus 1 to leave space for a null terminator) bytes from the sender if(bytesRcvd = recv(sock, echoBuffer, RCVBUFSIZE-1, 0) <= 0) DieWithError("recv() failed or connection closed prematurely"); totalBytesRcvd += bytesRcvd; // keep tally of total bytes echoBuffer[bytesRcvd] = '\0'; printf("%s", echoBuffer); // print the echo buffer } printf("\n"); closesocket(sock); WSACleanup(); exit(0); } void DieWithError(char *errorMessage) { fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); exit(1); } Server Code: // thanks cs.baylor.edu/~donahoo/practical/CSockets/code/TCPEchoServerWS.c #include <stdio.h> #include <winsock.h> #include <stdlib.h> #define MAXPENDING 5 // maximum outstanding connection requests #define RCVBUFSIZE 1000 void DieWithError(char *errorMessage); void HandleTCPClient(int clntSocket); // tcp client handling function int main(int argc, char **argv) { int serverSock; int clientSock; struct sockaddr_in echoServerAddr; struct sockaddr_in echoClientAddr; unsigned short echoServerPort; int clientLen; // length of client address data structure WSAData wsaData; if (argc!=2){ fprintf(stderr, "Usage: %s <Server Port>\n", argv[0]); exit(1); } echoServerPort = atoi(argv[1]); if(WSAStartup(MAKEWORD(2, 0), &wsaData)!=0){ fprintf(stderr, "WSAStartup() failed"); exit(1); } // create socket for incoming connections if((serverSock=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP))<0) DieWithError("socket() failed"); // construct local address structure memset(&echoServerAddr, 0, sizeof(echoServerAddr)); echoServerAddr.sin_family = AF_INET; echoServerAddr.sin_addr.s_addr = htonl(INADDR_ANY); // any incoming interface echoServerAddr.sin_port = htons(echoServerPort); // local port // bind to the local address if(bind(serverSock, (struct sockaddr*)&echoServerAddr, sizeof(echoServerAddr) )<0) DieWithError("bind() failed"); // mark the socket so it will listen for incoming connections if(listen(serverSock, MAXPENDING)<0) DieWithError("listen() failed"); for (;;){ // run forever // set the size of the in-out parameter clientLen = sizeof(echoClientAddr); // wait for a client to connect if((clientSock = accept(serverSock, (struct sockaddr*)&echoClientAddr, &clientLen)) < 0) DieWithError("accept() failed"); // clientSock is connected to a client printf("Handling client %s\n", inet_ntoa(echoClientAddr.sin_addr)); HandleTCPClient(clientSock); } // NOT REACHED } void DieWithError(char *errorMessage) { fprintf(stderr, "%s: %d\n", errorMessage, WSAGetLastError()); exit(1); } void HandleTCPClient(int clientSocket) { char echoBuffer[RCVBUFSIZE]; // buffer for echostring int recvMsgSize; // size of received message // receive message from client if((recvMsgSize = recv(clientSocket, echoBuffer, RCVBUFSIZE, 0) <0)) DieWithError("recv() failed"); // send received string and receive again until end of transmission while(recvMsgSize > 0){ // echo message back to client if(send(clientSocket, echoBuffer, recvMsgSize, 0)!=recvMsgSize) DieWithError("send() failed"); // see if there's more data to receive if((recvMsgSize = recv(clientSocket, echoBuffer, RCVBUFSIZE, 0)) <0) DieWithError("recv() failed"); } closesocket(clientSocket); // close client socket } How can I fix this?

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  • How do you handle live video streaming in Flash AS3?

    - by CodeJustin.com
    I've been dabbling with socket servers in Java and now I'm ready to get my feet wet with an idea I had. I would like to use python for my socket server and obviously AS3 for my client. I'm able to create a full chat using my own python socket server but I'm almost clueless what to do now that I want to add in LIVE video (want to make it a live video "chat"). I've found tutorials but they are for FMS and I can not afford that, also Red5 looked nice but couldn't find a live video tutorial off hand (plus I would have to switch to Red5 from my own socket server). So if someone could even nudge me into some resources on the subject (the subject of live video without using FMS) that would be very helpful, Google is failing me right now.

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  • MySQLPython is ignoring my my.cnf file. Where does it get its information?

    - by ?????
    When I try to use MySQLPython (via SQLAlchemy) I get the error File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/MySQL_python-1.2.3c1-py2.6-macosx-10.6-x86_64.egg/MySQLdb/connections.py", line 188, in __init__ super(Connection, self).__init__(*args, **kwargs2) sqlalchemy.exc.OperationalError: (OperationalError) (2002, "Can't connect to local MySQL server through socket '/opt/local/var/run/mysql5/mysqld.sock' (2)") None None but no other mysql client on my machine sees it fine! My my.cnf file states: [client] port = 3306 socket = /tmp/mysql/mysql.sock [safe_mysqld] socket = /tmp/mysql/mysql.sock [mysqld_safe] socket = /tmp/mysql/mysql.sock [mysqld] socket = /tmp/mysql/mysql.sock port = 3306 and the mysql.sock file is, indeed, located in /tmp/mysql I verified that ~/.my.cnf and /var/lib/mysql/my.cnf aren't overriding it. The mysql5 client program, etc, has no trouble connecting and neither does a groovy/grails installation on the same machine using jdbc/mysql connection thrilllap-2:~ swirsky$ mysql5 Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 6 Server version: 5.1.47 Source distribution Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved. This software comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to modify and redistribute it under the GPL v2 license Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | test | +--------------------+ 2 rows in set (0.00 sec) mysql> Why can't MySQLdb for python figure this out? Where would it look if not the my.cnf files?

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  • [C++][Boost] Acceptor and Problems with Async_Accept

    - by bobber205
    See code. :P I am able to receive new connections before async_accept() has been called. My delegate function is also never called so I can't manage any connections I receive, rendering the new connections useless. ;) So here's my question. Is there a way to prevent the Boost ASIO acceptor from getting new connections on its own and only getting connections from async_accept()? Thanks! bool AlexSocket::StartListening(int port) { bool didStart = false; if (!this->listening) { //try to listen acceptor = new tcp::acceptor(this->myService); boost::asio::ip::tcp::endpoint endpoint(boost::asio::ip::tcp::v4(), port); acceptor->open(endpoint.protocol()); acceptor->set_option(boost::asio::ip::tcp::acceptor::reuse_address(true)); acceptor->bind(endpoint); //CAN GET NEW CONNECTIONS HERE (before async_accept is called) acceptor->listen(); didStart = true; //probably change? tcp::socket* tempNewSocket = new tcp::socket(this->myService); acceptor->async_accept(*tempNewSocket, boost::bind(&AlexSocket::NewConnection, this, tempNewSocket, boost::asio::placeholders::error) ); } else //already started! return false; this->listening = didStart; return didStart; } //this function is never called :( void AlexSocket::NewConnection(tcp::socket* s, const boost::system::error_code& error) { cout << "New Connection Made" << endl; //Start new accept async tcp::socket* tempNewSocket = new tcp::socket(this->myService); acceptor->async_accept(*tempNewSocket, boost::bind(&AlexSocket::NewConnection, this, tempNewSocket, boost::asio::placeholders::error) ); }

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  • Analyzing Python Code: Modulus Operator

    - by Bhubhu Hbuhdbus
    I was looking at some code in Python (I know nothing about Python) and I came across this portion: def do_req(body): global host, req data = "" s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host, 80)) s.sendall(req % (len(body), body)) tmpdata = s.recv(8192) while len(tmpdata) > 0: data += tmpdata tmpdata = s.recv(8192) s.close() return data This is then called later on with body of huge size, as in over 500,000 bytes. This is sent to an Apache server that has the max request size on the default 8190 bytes. My question is what is happening at the "s.sendall()" part? Obviously the entire body cannot be sent at once and I'm guessing it is reduced by way of the modulus operator. I don't know how it works in Python, though. Can anyone explain? Thanks.

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  • Compiling linux library for mingw32

    - by TheFuzz
    I have been using a socket library for C++. Some other info: 32 bit Linux, Codelite and GCC toolset. I want to be able to compile my program for Windows using the windows edition of Codelite. The socket library I have been using doesn’t have a mingw32 build of the library, but it’s open source. So how can I make a mingw32 build of the socket library so I can make a windows build using the source provided?

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  • ZeroMQ REQ/REP on ipc:// and concurrency

    - by Metiu
    I implemented a JSON-RPC server using a REQ/REP 0MQ ipc:// socket and I'm experiencing strange behavior which I suspect is due to the fact that the ipc:// underlying unix socket is not a real socket, but rather a single pipe. From the documentation, one has to enforce strict zmq_send()/zmq_recv() alternation, otherwise the out-of-order zmq_send() will return an error. However, I expected the enforcement to be per-client, not per-socket. Of course with a Unix socket there is just one pipeline from multiple clients to the server, so the server won't know who it is talking with. Two clients could zmq_send() simultaneously and the server would see this as an alternation violation. The sequence could be: ClientA: zmq_send() ClientB: zmq_send() : will it block until the other send/receive completes? will it return -1? (I suspect it will with ipc:// due to inherent low-level problems, but with TCP it could distinguish the two clients) ClientA: zmq_recv() ClientB: zmq_recv() so what about tcp:// sockets? Will it work concurrently? Should I use some other locking mechanism to work around this?

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  • Code only runs properly if debugging step-by-step

    - by Cornwell
    Hello, I'm making a webserver and I've come up with some very strange problems. My server was running as expected yesterday when I turned off my laptop, but today it only sends the http headers (I didn't change anything) When a user requests a file, if I send them using the following code, it works perfectly: while ((n = fread(data, 1, sizeof(data), file)) > 0) send(ts, data, n, 0); but if I change it to this, it only sends ~2% of the file. And that's not a random number, it actually only sends about 2% of the file. while ((n = fread(data, 1, sizeof(data), file)) > 0) web.Send(data); int WEB::Send(string data) { return send(TempSocket, data.c_str(), data.size(), 0); } changing string to char* doesn't solve the problem. I'm using visual studio2010. If I run my code step-by-step, I am able to solve problem #1, everything gets sent. And that is my main problem. I do not understand why it happens. Hopefully someone can explain it to me. Thanks in advance. EDIT: int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrev, LPSTR lpCmd,int nShow) { SOCKET MainSocket=0; MSG msg; RedirectIOToConsole(); CreateThread(NULL, NULL, ListenThread, NULL, NULL, NULL); while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } WSACleanup(); closesocket(MainSocket); MainSocket = INVALID_SOCKET; return msg.wParam; } DWORD WINAPI ListenThread(LPVOID lparam) { SOCKET MainSocket; WSADATA wsaData; SOCKET tmpsock; struct sockaddr_in local, from; int fromlen=sizeof(from); WSAStartup(MAKEWORD(2, 2), &wsaData); local.sin_family=AF_INET; local.sin_addr.s_addr=INADDR_ANY; local.sin_port=htons(PORT); MainSocket=socket(AF_INET,SOCK_STREAM,0); if(MainSocket==INVALID_SOCKET) { return 0; } if(bind(MainSocket,(struct sockaddr*)&local,sizeof(local))!=0) { return 0; } if(listen(MainSocket,10)!=0) { return 0; } while(1) { tmpsock = accept(MainSocket,(struct sockaddr*)&from,&fromlen); CreateThread(NULL, NULL, SlaveThread, (LPVOID)tmpsock, NULL, NULL); } } DWORD WINAPI SlaveThread(LPVOID lparam) { SOCKET ts = (SOCKET)lparam;//temporary socket ...... char data[4096]; int n; unsigned long int length = statbuf.st_size; web.SendHeaders(200, "OK", format("Content-Disposition: attachment; filename=\"%s\"", FileName.c_str()).c_str(), web.GetMimeType(ReqPath.c_str()), length, statbuf.st_mtime); unsigned long int i=0,d=0; while ((n = fread(data, 1, sizeof(data), file)) > 0) { d+=send(ts, data, n, 0); i+=n; } printf("%i=%i=%i\n", length,i,d); fclose(file);

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  • How to hide helper functions from public API in c

    - by emge
    I'm working on a project and I need to create an API. I am using sockets to communicate between the server (my application) and the clients (the other applications using my API). This project is in c not C++ I come from a linux background and this is my first project using Windows, Visual Studio 2008, and dll libraries. I have communication working between the client and server, but I have some that is duplicated on both projects. I would like to create a library (probably a dll file), that both projects can link to so I don't have to maintain extra code. I also have to create the library that has the API that I need to make available for my clients. Within the API functions that I want public are the calls to these helper functions that are "duplicated code", I don't want to expose these functions to my client, but I do want my server to be able to use those functions. How can I do this? I will try to clarify with an example. This is what I started with. Server Project: int Server_GetPacket(SOCKET sd); int ReceiveAll(SOCKET sd, char *buf, int len); int VerifyLen(char *buf); Client Project: int Client_SendCommand(int command); int Client_GetData(int command, char *buf, int len); int ReceiveAll(SOCKET sd, char *buf, int len); int VerifyLen(char *buf); This is kind of what I would like to end up with: //Server Project: int Server_GetPacket(SOCKET sd); // library with public and private types // private API (not exposed to my client) int ReceiveAll(SOCKET sd, char *buf, int len); int VerifyLen(char *buf); // public API (header file available for client) int Client_SendCommand(int command); int Client_GetData(int command, char *buf, int len); Thanks any help would be appreciated.

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  • Multiple plugin instance loading with MEF

    - by Dave
    In my last application, using MEF to load plugins went just fine, but now I'm running into a new issue. I have a solution for it that I explain at the end of this question, but I'm looking for other ways to do it. Let's say I have an interface called ApplianceInterface. I also have two plugins that inherit from ApplianceInterface, let's call them Blender and Processor. Now, I would like to have multiple Blenders and Processors in my application, but I am not sure how to instantiate them properly. Before, I would simply use the ImportMany attribute and upon calling ComposeParts, my application would load Blender and Processor. For example: [ImportMany(typeof(ApplianceInterface))] private IEnumerable<ApplianceInterface> Appliances { get; set; } and my Blender and Processor plugins would be attributed like this: [PartCreationPolicy(CreationPolicy.NonShared)] [Export(typeof(MyInterface)] public class Blender : ApplianceInterface { ... } but what this ends up doing for me is populating Appliances with one Blender and one Processor. I need to be able to create an arbitrary number of Blender and Processor objects. Now, from the documentation I understand that [PartCreationPolicy(CreationPolicy.NonShared)] is what allows MEF to create a new instance each time, but is there a similar "magical" way to create a specific number of instances of something using MEF? Up until now, I've relied on [Import] and [ImportMany] to resolve the assemblies. Is my only option to use a global container, and then resolve the export manually using GetExportedValue<? I have tried GetExportedValue< and that implementation does work fine for me, but I was just curious if there is a better, more accepted way to do it.

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  • Splitting Code into Headers/Source files

    - by cam
    I took the following code from the examples page on Asio class tcp_connection : public boost::enable_shared_from_this<tcp_connection> { public: typedef boost::shared_ptr<tcp_connection> pointer; static pointer create(boost::asio::io_service& io_service) { return pointer(new tcp_connection(io_service)); } tcp::socket& socket() { return socket_; } void start() { message_ = make_daytime_string(); boost::asio::async_write(socket_, boost::asio::buffer(message_), boost::bind(&tcp_connection::handle_write, shared_from_this(), boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred)); } private: tcp_connection(boost::asio::io_service& io_service) : socket_(io_service) { } void handle_write(const boost::system::error_code& /*error*/, size_t /*bytes_transferred*/) { } tcp::socket socket_; std::string message_; }; I'm relatively new to C++ (from a C# background), and from what I understand, most people would split this into header and source files (declaration/implementation, respectively). Is there any reason I can't just leave it in the header file if I'm going to use it across many source files? If so, are there any tools that will automatically convert it to declaration/implementation for me? Can someone show me what this would look like split into header/source file for an example (or just part of it, anyway)? I get confused around weird stuff like thistypedef boost::shared_ptr<tcp_connection> pointer; Do I include this in the header or the source? Same with tcp::socket& socket() I've read many tutorials, but this has always been something that has confused me about C++.

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  • Where to begin with multi-threaded programming with c++?

    - by zoke
    I'm trying to implement my own IRC client as a personal proejct and I realized I needed a way to read and write from the socket at the same time. I realized I could have a reading thread which reads from the socket in the background and puts data in a queue and I could have another thread which writes data from a queue to the socket. However I have no idea on how to start with multithreaded programing or how to do it with c++. Where do I go from here?

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  • C++ MFC server app with sockets crashes and I cannot find the fault, help!

    - by usermeister
    My program has one dialog and two sockets. Both sockets are derived from CAsyncSocket, one is for listening, other is for receiving data from client. My program crashes when client tries to connect to server application and server needs to initialize receiving socket. This is my MFC dialog class. class CFileTransferServerDlg : public CDialog { ... ListeningSocket ListenSock; ReceivingSocket* RecvSock; void OnAccept(); // called when ListenSock gets connection attempt ... }; This is my derived socket class for receiving data that calls parent dialogs method when event is signaled. class ReceivingSocket : public CAsyncSocket { CFileTransferServerDlg* m_pDlg; // for accessing parent dialogs controls virtual void OnReceive(int nErrorCode); } ReceivingSocket::ReceivingSocket() { } This is dialogs function that handles incoming connection attempt when listening socket gets event notification. This is where the crash happens. void CFileTransferServerDlg::OnAccept() { RecvSock = new ReceivingSocket; /* CRASH */ } OR void CFileTransferServerDlg::OnAccept() { ReceivingSocket* tmpSock = new ReceivingSocket; tmpSock->SetParentDlg(this); CString message; if( ListenSock.Accept(*tmpSock) ) /* CRASH */ { message.LoadStringW(IDS_CLIENT_CONNECTED); m_txtStatus.SetWindowTextW(message); RecvSock = tmpSock; } } My program crashes when I try to create a socket for receiving file sent from client application. OnAccept starts when Listening socket signals incoming connection attempt, but my application then crashes. I've tried running it on another computer and connection attempt was succesful. What could be wrong? Error in debug mode: Unhandled exception at 0x009c30e1 in FileTransferServer.exe: 0xC0000005: Access violation reading location 0xccccce58.

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  • Problems with Asynchronous UDP Sockets

    - by ihatenetworkcoding
    Hi, I'm struggling a bit with socket programming (something I'm not at all familiar with) and I can't find anything which helps from google or MSDN (awful). Apologies for the length of this. Basically I have an existing service which recieves and responds to requests over UDP. I can't change this at all. I also have a client within my webapp which dispatches and listens for responses to that service. The existing client I've been given is a singleton which creates a socket and an array of response slots, and then creates a background thread with an infinite looping method that makes "sock.Receive()" calls and pushes the data received into the slot array. All kinds of things about this seem wrong to me and the infinite thread breaks my unit testing so I'm trying to replace this service with one which makes it's it's send/receives asynchronously instead. Point 1: Is this the right approach? I want a non-blocking, scalable, thread-safe service. My first attempt is roughly like this, which sort of worked but the data I got back was always shorter than expected (i.e. the buffer did not have the number of bytes requested) and seemed to throw exceptions when processed. private Socket MyPreConfiguredSocket; public object Query() { //build a request this.MyPreConfiguredSocket.SendTo(MYREQUEST, packet.Length, SocketFlags.Multicast, this._target); IAsyncResult h = this._sock.BeginReceiveFrom(response, 0, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), this._sock); if (!h.AsyncWaitHandle.WaitOne(TIMEOUT)) { throw new Exception("Timed out"); } //process response data (always shortened) } private void ARecieve (IAsyncResult result) { int bytesreceived = (result as Socket).EndReceiveFrom(result, ref this._target); } My second attempt was based on more google trawling and this recursive pattern I frequently saw, but this version always times out! It never gets to ARecieve. public object Query() { //build a request this.MyPreConfiguredSocket.SendTo(MYREQUEST, packet.Length, SocketFlags.Multicast, this._target); State s = new State(this.MyPreConfiguredSocket); this.MyPreConfiguredSocket.BeginReceiveFrom(s.Buffer, 0, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), s); if (!s.Flag.WaitOne(10000)) { throw new Exception("Timed out"); } //always thrown //process response data } private void ARecieve (IAsyncResult result) { //never gets here! State s = (result as State); int bytesreceived = s.Sock.EndReceiveFrom(result, ref this._target); if (bytesreceived > 0) { s.Received += bytesreceived; this._sock.BeginReceiveFrom(s.Buffer, s.Received, BUFFER_SIZE, SocketFlags.None, ref this._target, new AsyncCallback(ARecieve), s); } else { s.Flag.Set(); } } private class State { public State(Socket sock) { this._sock = sock; this._buffer = new byte[BUFFER_SIZE]; this._buffer.Initialize(); } public Socket Sock; public byte[] Buffer; public ManualResetEvent Flag = new ManualResetEvent(false); public int Received = 0; } Point 2: So clearly I'm getting something quite wrong. Point 3: I'm not sure if I'm going about this right. How does the data coming from the remote service even get to the right listening thread? Do I need to create a socket per request? Out of my comfort zone here. Need help.

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  • How Do Sockets Work in C?

    - by kaybenleroll
    I am a bit confused about socket programming in C. You create a socket, bind it to an interface and an IP address and get it to listen. I found a couple of web resources on that, and understood it fine. In particular, I found an article Network programming under Unix systems to be very informative. What confuses me is the timing of data arriving on the socket. How can you tell when packets arrive, and how big the packet is, do you have to do all the heavy lifting yourself? My basic assumption here is that packets can be of variable length, so once binary data starts appearing down the socket, how do you begin to construct packets from that?

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  • Detecting TCP dropout over an unreliable network

    - by yx
    I am doing some experimentation over an unreliable radio network (home brewed) using very rudimentary java socket programming to transfer messages back and forth between the end nodes. The setup is as follows: Node A --- Relay Node --- Node B One problem I am constantly running into is that somehow the connection drops out and neither Node A or B knows that the link is dead, and yet continues to transmit data. The TCP connection does not time out either. I have added in a heartbeat message that causes a timeout after a while, but I still would like to know what is the underlying cause of why TCP does not time out. Here are the options I am enabling when setting up a socket: channel.socket().setKeepAlive(false); channel.socket().setTrafficClass(0x08); // for max throughput This behavior is strange since it is totally different than when I have a wired network. On a wired network, I can simulate a disconnected connection by pulling out the ethernet cord, however, once I plug the cord back in, the connection becomes restablished and messages begin to be passed through once more. On the radio network, the connection is never reestablished and once it silently dies, the messages never resume. Is there some other unknown java implentation or setting for a socket that I can use, also, why am I seeing this behavior in the first place? And yes, before anyone says anything, I know TCP is not the preffered choice over an unreliable network, but in this case I wanted to ensure no packet loss.

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  • TDD, Unit Test and architectural changes

    - by Leandro
    I'm writing an RPC middleware in C++. I have a class named RPCClientProxy that contains a socket client inside: class RPCClientProxy { ... private: Socket* pSocket; ... } The constructor: RPCClientProxy::RPCClientProxy(host, port) { pSocket = new Socket(host, port); } As you can see, I don't need to tell the user that I have a socket inside. Although, to make unit tests for my proxies it would be necessary to create mocks for sockets and pass them to the proxies, and to do so I must use a setter or pass a factory to the sockets in the proxies's constructors. My question: According to TDD, is it acceptable to do it ONLY because the tests? As you can see, these changes would change the way the library is used by a programmer.

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  • BluetoothChat doesn't work

    - by jes
    Hello I want to make conversation between android devices. I use BluetoothChat to do this but it doesn't work I can't read correctly data from another device. Conversation is : Me: privet Device: p Device: rivet Can you help me? private class ConnectedThread extends Thread { private final InputStream mmInStream; private final OutputStream mmOutStream; public ConnectedThread(BluetoothSocket socket) { Log.d(TAG, "create ConnectedThread"); mmSocket = socket; //InputStream tmpIn = null; OutputStream tmpOut = null; BufferedInputStream tmpIn=null; int INPUT_BUFFER_SIZE=32; // Get the BluetoothSocket input and output streams try { //tmpIn = socket.getInputStream(); tmpOut = socket.getOutputStream(); tmpIn = new BufferedInputStream(socket.getInputStream(),INPUT_BUFFER_SIZE); } catch (IOException e) { Log.e(TAG, "temp sockets not created", e); } mmInStream = tmpIn; mmOutStream = tmpOut; } public void run() { Log.i(TAG, "BEGIN mConnectedThread"); byte[] buffer = new byte[1024]; int bytes; // Keep listening to the InputStream while connected while (true) { try { // Read from the InputStream bytes = mmInStream.read(buffer); // Send the obtained bytes to the UI Activity mHandler.obtainMessage(BluetoothChat.MESSAGE_READ, bytes, -1, buffer) .sendToTarget(); } catch (IOException e) { Log.e(TAG, "disconnected", e); connectionLost(); break; } } }

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  • Select where a value present

    - by Roy
    First a database example: id, product_id, cat, name, value -------------------------------- 1,1,Algemeen,Processor,2 Ghz 2,1,Algemeen,Geheugen,4 GB 3,2,Algemeen,Processor,3 Ghz 4,2,Algemeen,Geheugen,4 GB 5,3,Beeldscherm,Inch,22" 6,3,Beeldscherm,Kleur,Zwart 7,3,Algemeen,Geheugen,3 GB 8,3,Algemeen,Processor,3 Ghz I want with one query to select the follow id's: 1,2,3,4,7,8 Because the cat = algemeen and the name = processor by these products. ID 5,6 are only present by product 3. So, the entry's (cat and name) which are present by all products (product_id) have to be selected. The database contains 80.000 entry's with a lot of diffrent cat's, name's and value's. Is this possible with one query or is some php necessary? How do I do this? My apologies for the bad English.

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  • How to setup stunnel so that gmail can use my own smtp server to send messages.

    - by igorhvr
    I am trying to setup gmail to send messages using my own smtp server. I am doing this by using stunnel over a non-ssl enabled server. I am able to use my own smtp client with ssl enabled just fine to my server. Unfortunately, however, gmail seems to be unable to connect to my stunnel port. Gmail seems to be simply closing the connection right after it is established - I get a "SSL socket closed on SSL_read" on my server logs. On gmail, I get a "We are having trouble authenticating with your other mail service. Please try changing your SSL settings. If you continue to experience difficulties, please contact your other email provider for further instructions." message. Any help / tips on figuring this out will be appreciated. My certificate is self-signed - could this perhaps be related to the problem I am experiencing? I pasted the entire SSL session (logs from my server) below. 2011.01.02 16:56:20 LOG7[20897:3082491584]: Service ssmtp accepted FD=0 from 209.85.210.171:46858 2011.01.02 16:56:20 LOG7[20897:3082267504]: Service ssmtp started 2011.01.02 16:56:20 LOG7[20897:3082267504]: FD=0 in non-blocking mode 2011.01.02 16:56:20 LOG7[20897:3082267504]: Option TCP_NODELAY set on local socket 2011.01.02 16:56:20 LOG7[20897:3082267504]: Waiting for a libwrap process 2011.01.02 16:56:20 LOG7[20897:3082267504]: Acquired libwrap process #0 2011.01.02 16:56:20 LOG7[20897:3082267504]: Releasing libwrap process #0 2011.01.02 16:56:20 LOG7[20897:3082267504]: Released libwrap process #0 2011.01.02 16:56:20 LOG7[20897:3082267504]: Service ssmtp permitted by libwrap from 209.85.210.171:46858 2011.01.02 16:56:20 LOG5[20897:3082267504]: Service ssmtp accepted connection from 209.85.210.171:46858 2011.01.02 16:56:20 LOG7[20897:3082267504]: FD=1 in non-blocking mode 2011.01.02 16:56:20 LOG6[20897:3082267504]: connect_blocking: connecting 127.0.0.1:25 2011.01.02 16:56:20 LOG7[20897:3082267504]: connect_blocking: s_poll_wait 127.0.0.1:25: waiting 10 seconds 2011.01.02 16:56:20 LOG5[20897:3082267504]: connect_blocking: connected 127.0.0.1:25 2011.01.02 16:56:20 LOG5[20897:3082267504]: Service ssmtp connected remote server from 127.0.0.1:3701 2011.01.02 16:56:20 LOG7[20897:3082267504]: Remote FD=1 initialized 2011.01.02 16:56:20 LOG7[20897:3082267504]: Option TCP_NODELAY set on remote socket 2011.01.02 16:56:20 LOG5[20897:3082267504]: Negotiations for smtp (server side) started 2011.01.02 16:56:20 LOG7[20897:3082267504]: RFC 2487 not detected 2011.01.02 16:56:20 LOG5[20897:3082267504]: Protocol negotiations succeeded 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): before/accept initialization 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 read client hello A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 write server hello A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 write certificate A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 write certificate request A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 flush data 2011.01.02 16:56:20 LOG5[20897:3082267504]: CRL: verification passed 2011.01.02 16:56:20 LOG5[20897:3082267504]: VERIFY OK: depth=2, /C=US/O=Equifax/OU=Equifax Secure Certificate Authority 2011.01.02 16:56:20 LOG5[20897:3082267504]: CRL: verification passed 2011.01.02 16:56:20 LOG5[20897:3082267504]: VERIFY OK: depth=1, /C=US/O=Google Inc/CN=Google Internet Authority 2011.01.02 16:56:20 LOG5[20897:3082267504]: CRL: verification passed 2011.01.02 16:56:20 LOG5[20897:3082267504]: VERIFY OK: depth=0, /C=US/ST=California/L=Mountain View/O=Google Inc/CN=smtp.gmail.com 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 read client certificate A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 read client key exchange A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 read certificate verify A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 read finished A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 write change cipher spec A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 write finished A 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL state (accept): SSLv3 flush data 2011.01.02 16:56:20 LOG7[20897:3082267504]: 1 items in the session cache 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 client connects (SSL_connect()) 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 client connects that finished 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 client renegotiations requested 2011.01.02 16:56:20 LOG7[20897:3082267504]: 1 server connects (SSL_accept()) 2011.01.02 16:56:20 LOG7[20897:3082267504]: 1 server connects that finished 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 server renegotiations requested 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 session cache hits 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 external session cache hits 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 session cache misses 2011.01.02 16:56:20 LOG7[20897:3082267504]: 0 session cache timeouts 2011.01.02 16:56:20 LOG6[20897:3082267504]: SSL accepted: new session negotiated 2011.01.02 16:56:20 LOG6[20897:3082267504]: Negotiated ciphers: RC4-MD5 SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=MD5 2011.01.02 16:56:20 LOG7[20897:3082267504]: SSL socket closed on SSL_read 2011.01.02 16:56:20 LOG7[20897:3082267504]: Socket write shutdown 2011.01.02 16:56:20 LOG5[20897:3082267504]: Connection closed: 167 bytes sent to SSL, 37 bytes sent to socket 2011.01.02 16:56:20 LOG7[20897:3082267504]: Service ssmtp finished (0 left)

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