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• How to use CFNetwork to get byte array from sockets?

  - by Vic

  Hi, I'm working in a project for the iPad, it is a small program and I need it to communicate with another software that runs on windows and act like a server; so the application that I'm creating for the iPad will be the client. I'm using CFNetwork to do sockets communication, this is the way I'm establishing the connection: char ip[] = "192.168.0.244"; NSString *ipAddress = [[NSString alloc] initWithCString:ip]; /* Build our socket context; this ties an instance of self to the socket */ CFSocketContext CTX = { 0, self, NULL, NULL, NULL }; /* Create the server socket as a TCP IPv4 socket and set a callback */ /* for calls to the socket's lower-level connect() function */ TCPClient = CFSocketCreate(NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketDataCallBack, (CFSocketCallBack)ConnectCallBack, &CTX); if (TCPClient == NULL) return; /* Set the port and address we want to listen on */ struct sockaddr_in addr; memset(&addr, 0, sizeof(addr)); addr.sin_len = sizeof(addr); addr.sin_family = AF_INET; addr.sin_port = htons(PORT); addr.sin_addr.s_addr = inet_addr([ipAddress UTF8String]); CFDataRef connectAddr = CFDataCreate(NULL, (unsigned char *)&addr, sizeof(addr)); CFSocketConnectToAddress(TCPClient, connectAddr, -1); CFRunLoopSourceRef sourceRef = CFSocketCreateRunLoopSource(kCFAllocatorDefault, TCPClient, 0); CFRunLoopAddSource(CFRunLoopGetCurrent(), sourceRef, kCFRunLoopCommonModes); CFRelease(sourceRef); CFRunLoopRun(); And this is the way I sent the data, which basically is a byte array /* The native socket, used for various operations */ // TCPClient is a CFSocketRef member variable CFSocketNativeHandle sock = CFSocketGetNative(TCPClient); Byte byteData[3]; byteData[0] = 0; byteData[1] = 4; byteData[2] = 0; send(sock, byteData, strlen(byteData)+1, 0); Finally, as you may have noticed, when I create the server socket, I registered a callback for the kCFSocketDataCallBack type, this is the code. void ConnectCallBack(CFSocketRef socket, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) { // SocketsViewController is the class that contains all the methods SocketsViewController *obj = (SocketsViewController*)info; UInt8 *unsignedData = (UInt8 *) CFDataGetBytePtr(data); char *value = (char*)unsignedData; NSString *text = [[NSString alloc]initWithCString:value length:strlen(value)]; [obj writeToTextView:text]; [text release]; } Actually, this callback is being invoked in my code, the problem is that I don't know how can I get the data that the windows client sent me, I'm expecting to receive an array of bytes, but I don't know how can I get those bytes from the data param. If anyone can help me to find a way to do this, or maybe me point me to another way to get the data from the server in my client application I would really appreciate it. Thanks.

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• Sockets, Threads and Services in android, how to make them work together ?

  - by Spredzy

  Hi all, I am facing a probleme with threads and sockets I cant figure it out, if someone can help me please i would really appreciate. There are the facts : I have a service class NetworkService, inside this class I have a Socket attribute. I would like it be at the state of connected for the whole lifecycle of the service. To connect the socket I do it in a thread, so if the server has to timeout, it would not block my UI thread. Problem is, into the thread where I connect my socket everything is fine, it is connected and I can talk to my server, once this thread is over and I try to reuse the socket, in another thread, I have the error message Socket is not connected. Questions are : - Is the socket automatically disconnected at the end of the thread? - Is their anyway we can pass back a value from a called thread to the caller ? Thanks a lot, Here is my code public class NetworkService extends Service { private Socket mSocket = new Socket(); private void _connectSocket(String addr, int port) { Runnable connect = new connectSocket(this.mSocket, addr, port); new Thread(connect).start(); } private void _authentification() { Runnable auth = new authentification(); new Thread(auth).start(); } private INetwork.Stub mBinder = new INetwork.Stub() { @Override public int doConnect(String addr, int port) throws RemoteException { _connectSocket(addr, port); _authentification(); return 0; } }; class connectSocket implements Runnable { String addrSocket; int portSocket; int TIMEOUT=5000; public connectSocket(String addr, int port) { addrSocket = addr; portSocket = port; } @Override public void run() { SocketAddress socketAddress = new InetSocketAddress(addrSocket, portSocket); try { mSocket.connect(socketAddress, TIMEOUT); PrintWriter out = new PrintWriter(mSocket.getOutputStream(), true); out.println("test42"); Log.i("connectSocket()", "Connection Succesful"); } catch (IOException e) { Log.e("connectSocket()", e.getMessage()); e.printStackTrace(); } } } class authentification implements Runnable { private String constructFirstConnectQuery() { String query = "toto"; return query; } @Override public void run() { BufferedReader in; PrintWriter out; String line = ""; try { in = new BufferedReader(new InputStreamReader(mSocket.getInputStream())); out = new PrintWriter(mSocket.getOutputStream(), true); out.println(constructFirstConnectQuery()); while (mSocket.isConnected()) { line = in.readLine(); Log.e("LINE", "[Current]- " + line); } } catch (IOException e) {e.printStackTrace();} } }

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• Compatibility between Qt and Boost sockets libraries

  - by cake

  Hello In my work, I'm developing a Viewer client for a Offshore simulation server, using sockets to send the simulation data from the Simulator to de Viewer. But, the server uses Boost.asio as it's sockets library. As the client uses Qt for it's GUI, I was wondering if there is any problem in using de Qt Networking library for handling the sockets. Is there any compatibility issues? Thanks in advance, and sorry for my bad english.

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

  - by Roman

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

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• Apache2 + FCGI + PHP5 not creating sockets / pools

  - by CodyRo

  I have a pretty vanilla setup with Apache2, FastCGI setup as DSO and serving PHP through an external CGI script that sets the max children / serves the request to PHP. The issue is FastCGI doesn't appear to be creating the PHP sockets / pooling them so each request calls the php-cgi binary, then dies off .. effectively making the reason I want to use FastCGI moot. The only configuration directives I have are: AddHandler php5-fastcgi .php Action php5-fastcgi /cgi-bin/fcgi.cgi FastCgiIpcDir /usr/local/apache2/fastcgi The dyanmic/ directory is getting created as anticipated, but there are no sockets in there. Permissions are indeed correct. Any help would be greatly appreciated, thanks!

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• C sockets, chat server and client, problem echoing back.

  - by wretrOvian

  Hi This is my chat server : #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define LISTEN_Q 20 #define MSG_SIZE 1024 struct userlist { int sockfd; struct sockaddr addr; struct userlist *next; }; int main(int argc, char *argv[]) { // declare. int listFD, newFD, fdmax, i, j, bytesrecvd; char msg[MSG_SIZE], ipv4[INET_ADDRSTRLEN]; struct addrinfo hints, *srvrAI; struct sockaddr_storage newAddr; struct userlist *users, *uptr, *utemp; socklen_t newAddrLen; fd_set master_set, read_set; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // create a user list users = (struct userlist *)malloc(sizeof(struct userlist)); users->sockfd = -1; //users->addr = NULL; users->next = NULL; // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo("localhost", argv[1], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((listFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // bind socket bind(listFD, srvrAI->ai_addr, srvrAI->ai_addrlen); // listen on socket if(listen(listFD, LISTEN_Q) == -1) { perror("* ERROR | listen()\n"); exit(1); } // add listfd to master_set FD_SET(listFD, &master_set); // initialize fdmax fdmax = listFD; while(1) { // equate read_set = master_set; // run select if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()\n"); exit(1); } // query all sockets for(i = 0; i <= fdmax; i++) { if(FD_ISSET(i, &read_set)) { // found active sockfd if(i == listFD) { // new connection // accept newAddrLen = sizeof newAddr; if((newFD = accept(listFD, (struct sockaddr *)&newAddr, &newAddrLen)) == -1) { perror("* ERROR | select()\n"); exit(1); } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&newAddr)->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } fprintf(stdout, "* Client Connected | %s\n", ipv4); // add to master list FD_SET(newFD, &master_set); // create new userlist component utemp = (struct userlist*)malloc(sizeof(struct userlist)); utemp->next = NULL; utemp->sockfd = newFD; utemp->addr = *((struct sockaddr *)&newAddr); // iterate to last node for(uptr = users; uptr->next != NULL; uptr = uptr->next) { } // add uptr->next = utemp; // update fdmax if(newFD > fdmax) fdmax = newFD; } else { // existing sockfd transmitting data // read if((bytesrecvd = recv(i, msg, MSG_SIZE, 0)) == -1) { perror("* ERROR | recv()\n"); exit(1); } msg[bytesrecvd] = '\0'; // find out who sent? for(uptr = users; uptr->next != NULL; uptr = uptr->next) { if(i == uptr->sockfd) break; } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&(uptr->addr))->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } // print fprintf(stdout, "%s\n", msg); // send to all for(j = 0; j <= fdmax; j++) { if(FD_ISSET(j, &master_set)) { if(send(j, msg, strlen(msg), 0) == -1) perror("* ERROR | send()"); } } } // handle read from client } // end select result handle } // end looping fds } // end while return 0; } This is my client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define MSG_SIZE 1024 int main(int argc, char *argv[]) { // declare. int newFD, bytesrecvd, fdmax; char msg[MSG_SIZE]; fd_set master_set, read_set; struct addrinfo hints, *srvrAI; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo(argv[1], argv[2], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((newFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // connect to server if(connect(newFD, srvrAI->ai_addr, srvrAI->ai_addrlen) == -1) { perror("* ERROR | connect()\n"); exit(1); } // add to master, and add keyboard FD_SET(newFD, &master_set); FD_SET(STDIN_FILENO, &master_set); // initialize fdmax if(newFD > STDIN_FILENO) fdmax = newFD; else fdmax = STDIN_FILENO; while(1) { // equate read_set = master_set; if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()"); exit(1); } // check server if(FD_ISSET(newFD, &read_set)) { // read data if((bytesrecvd = recv(newFD, msg, MSG_SIZE, 0)) < 0 ) { perror("* ERROR | recv()"); exit(1); } msg[bytesrecvd] = '\0'; // print fprintf(stdout, "%s\n", msg); } // check keyboard if(FD_ISSET(STDIN_FILENO, &read_set)) { // read data from stdin if((bytesrecvd = read(STDIN_FILENO, msg, MSG_SIZE)) < 0) { perror("* ERROR | read()"); exit(1); } msg[bytesrecvd] = '\0'; // send if((send(newFD, msg, bytesrecvd, 0)) == -1) { perror("* ERROR | send()"); exit(1); } } } return 0; } The problem is with the part where the server recv()s data from an FD, then tries echoing back to all [send() ]; it just dies, w/o errors, and my client is left looping :(

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• Sending large serialized objects over sockets is failing only when trying to grow the byte Array, bu

  - by FinancialRadDeveloper

  I have code where I am trying to grow the byte array while receiving the data over my socket. This is erroring out. public bool ReceiveObject2(ref Object objRec, ref string sErrMsg) { try { byte[] buffer = new byte[1024]; byte[] byArrAll = new byte[0]; bool bAllBytesRead = false; int iRecLoop = 0; // grow the byte array to match the size of the object, so we can put whatever we // like through the socket as long as the object serialises and is binary formatted while (!bAllBytesRead) { if (m_socClient.Receive(buffer) > 0) { byArrAll = Combine(byArrAll, buffer); iRecLoop++; } else { m_socClient.Close(); bAllBytesRead = true; } } MemoryStream ms = new MemoryStream(buffer); BinaryFormatter bf1 = new BinaryFormatter(); ms.Position = 0; Object obj = bf1.Deserialize(ms); objRec = obj; return true; } catch (System.Runtime.Serialization.SerializationException se) { objRec = null; sErrMsg += "SocketClient.ReceiveObject " + "Source " + se.Source + "Error : " + se.Message; return false; } catch (Exception e) { objRec = null; sErrMsg += "SocketClient.ReceiveObject " + "Source " + e.Source + "Error : " + e.Message; return false; } } private byte[] Combine(byte[] first, byte[] second) { byte[] ret = new byte[first.Length + second.Length]; Buffer.BlockCopy(first, 0, ret, 0, first.Length); Buffer.BlockCopy(second, 0, ret, first.Length, second.Length); return ret; } Error: mscorlibError : The input stream is not a valid binary format. The starting contents (in bytes) are: 68-61-73-43-68-61-6E-67-65-73-3D-22-69-6E-73-65-72 ... Yet when I just cheat and use a MASSIVE buffer size its fine. public bool ReceiveObject(ref Object objRec, ref string sErrMsg) { try { byte[] buffer = new byte[5000000]; m_socClient.Receive(buffer); MemoryStream ms = new MemoryStream(buffer); BinaryFormatter bf1 = new BinaryFormatter(); ms.Position = 0; Object obj = bf1.Deserialize(ms); objRec = obj; return true; } catch (Exception e) { objRec = null; sErrMsg += "SocketClient.ReceiveObject " + "Source " + e.Source + "Error : " + e.Message; return false; } } This is really killing me. I don't know why its not working. I have lifted the Combine from a suggestion on here too, so I am pretty sure this is not doing the wrong thing? I hope someone can point out where I am going wrong

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• What is stopping data flow with .NET 3.5 asynchronous System.Net.Sockets.Socket?

  - by TonyG

  I have a .NET 3.5 client/server socket interface using the asynchronous methods. The client connects to the server and the connection should remain open until the app terminates. The protocol consists of the following pattern: send stx receive ack send data1 receive ack send data2 (repeat 5-6 while more data) receive ack send etx So a single transaction with two datablocks as above would consist of 4 sends from the client. After sending etx the client simply waits for more data to send out, then begins the next transmission with stx. I do not want to break the connection between individual exchanges or after each stx/data/etx payload. Right now, after connection, the client can send the first stx, and get a single ack, but I can't put more data onto the wire after that. Neither side disconnects, the socket is still intact. The client code is seriously abbreviated as follows - I'm following the pattern commonly available in online code samples. private void SendReceive(string data) { // ... SocketAsyncEventArgs completeArgs; completeArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnSend); clientSocket.SendAsync(completeArgs); // two AutoResetEvents, one for send, one for receive if ( !AutoResetEvent.WaitAll(autoSendReceiveEvents , -1) ) Log("failed"); else Log("success"); // ... } private void OnSend( object sender , SocketAsyncEventArgs e ) { // ... Socket s = e.UserToken as Socket; byte[] receiveBuffer = new byte[ 4096 ]; e.SetBuffer(receiveBuffer , 0 , receiveBuffer.Length); e.Completed += new EventHandler<SocketAsyncEventArgs>(OnReceive); s.ReceiveAsync(e); // ... } private void OnReceive( object sender , SocketAsyncEventArgs e ) {} // ... if ( e.BytesTransferred > 0 ) { Int32 bytesTransferred = e.BytesTransferred; String received = Encoding.ASCII.GetString(e.Buffer , e.Offset , bytesTransferred); dataReceived += received; } autoSendReceiveEvents[ SendOperation ].Set(); // could be moved elsewhere autoSendReceiveEvents[ ReceiveOperation ].Set(); // releases mutexes } The code on the server is very similar except that it receives first and then sends a response - the server is not doing anything (that I can tell) to modify the connection after it sends a response. The problem is that the second time I hit SendReceive in the client, the connection is already in a weird state. Do I need to do something in the client to preserve the SocketAsyncEventArgs, and re-use the same object for the lifetime of the socket/connection? I'm not sure which eventargs object should hang around during the life of the connection or a given exchange. Do I need to do something, or Not do something in the server to ensure it continues to Receive data? The server setup and response processing looks like this: void Start() { // ... listenSocket.Bind(...); listenSocket.Listen(0); StartAccept(null); // note accept as soon as we start. OK? mutex.WaitOne(); } void StartAccept(SocketAsyncEventArgs acceptEventArg) { if ( acceptEventArg == null ) { acceptEventArg = new SocketAsyncEventArgs(); acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(OnAcceptCompleted); } Boolean willRaiseEvent = this.listenSocket.AcceptAsync(acceptEventArg); if ( !willRaiseEvent ) ProcessAccept(acceptEventArg); // ... } private void OnAcceptCompleted( object sender , SocketAsyncEventArgs e ) { ProcessAccept(e); } private void ProcessAccept( SocketAsyncEventArgs e ) { // ... SocketAsyncEventArgs readEventArgs = new SocketAsyncEventArgs(); readEventArgs.SetBuffer(dataBuffer , 0 , Int16.MaxValue); readEventArgs.Completed += new EventHandler<SocketAsyncEventArgs>(OnIOCompleted); readEventArgs.UserToken = e.AcceptSocket; dataReceived = ""; // note server is degraded for single client/thread use // As soon as the client is connected, post a receive to the connection. Boolean willRaiseEvent = e.AcceptSocket.ReceiveAsync(readEventArgs); if ( !willRaiseEvent ) this.ProcessReceive(readEventArgs); // Accept the next connection request. this.StartAccept(e); } private void OnIOCompleted( object sender , SocketAsyncEventArgs e ) { // switch ( e.LastOperation ) case SocketAsyncOperation.Receive: ProcessReceive(e); // similar to client code // operate on dataReceived here case SocketAsyncOperation.Send: ProcessSend(e); // similar to client code } // execute this when a data has been processed into a response (ack, etc) private SendResponseToClient(string response) { // create buffer with response // currentEventArgs has class scope and is re-used currentEventArgs.SetBuffer(sendBuffer , 0 , sendBuffer.Length); Boolean willRaiseEvent = currentClient.SendAsync(currentEventArgs); if ( !willRaiseEvent ) ProcessSend(currentEventArgs); } A .NET trace shows the following when sending ABC\r\n: Socket#7588182::SendAsync() Socket#7588182::SendAsync(True#1) Data from Socket#7588182::FinishOperation(SendAsync) 00000000 : 41 42 43 0D 0A Socket#7588182::ReceiveAsync() Exiting Socket#7588182::ReceiveAsync() - True#1 And it stops there. It looks just like the first send from the client but the server shows no activity. I think that could be info overload for now but I'll be happy to provide more details as required. Thanks!

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• How to handle activity life cycle involving sockets in Android?

  - by Henrik

  Hello all, I have an Android activity which in turn starts a thread. In the thread I open a persistent TCP socket connection. When the socket connects to the server dynamic data is downloaded. The thread sends messages using Handler-class to the activity when data has been received. Now if the user happens to switch from portrait to landscape mode the activity gets an onDestroy call. At this moment I close the socket and stop the thread. When Android has switched landscape mode it calls onCreate yet again and I have to do a socket re-connect. Also, all of the data the activity received needs to be downloaded once more because the server does not have the ability to know what has been sent before, i.e. there is no "resume" feature. Thus the problem is that there is alot of data which is resent all the time when landscape mode is changed. What are my options here? Should I create a service which handles the socket traffic towards the server thus I always got all the data which the server has sent in the service. Or should I disable landscape mode all together perhaps? Or would my best bet be to rewrite my server which is a VERY BIG job :-) All input is welcome :-) / Henrik

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• Know if the client has terminated while using sockets in C..

  - by shadyabhi

  Suppose, I have a connected socket after writing this code.. if ((sd = accept(socket_d, (struct sockaddr *)&client_addr, &alen)) < 0) { perror("accept failed\n"); exit(1); } How can I know at the server side that client has exited.

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• CLOSE_WAIT sockets burst - perhaps because of iptables settings?

  - by Fabrizio Giudici

  I have an Ubuntu 12.04 server virtual box where basically the installed software and configuration are the default ones, plus the installation of a jetty 6 server which servers a few websites. To keep things simple I didn't install apache httpd and used iptables for exposing jetty (which runs on the 8080 port) to the port 80. These are the results of /sbin/iptables -t nat -L Chain PREROUTING (policy ACCEPT) target prot opt source destination REDIRECT tcp -- anywhere localhost tcp dpt:http redir ports 8080 REDIRECT tcp -- anywhere Ubuntu-1104-natty-64-minimal tcp dpt:http redir ports 8080 Chain INPUT (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination REDIRECT tcp -- anywhere localhost tcp dpt:http redir ports 8080 REDIRECT tcp -- anywhere Ubuntu-1104-natty-64-minimal tcp dpt:http redir ports 8080 Chain POSTROUTING (policy ACCEPT) target prot opt source destination I must confess I have a shallow comprehension of how iptables works, in particular for the different kind of chains. This thing works, but sometimes I have an explosion of sockets that stay permanently in CLOSE_WAIT state. I know about what this state means, but since I didn't write the code that manages servlets (they are handled by jetty) I can't fix the problem by patching my code. Eventually the amount of CLOSE_WAIT sockets builds up and makes the server not responsive, so I have to restart jetty. I've looked around for similar problems wth CLOSE_WAIT, and only found cases related to the programmer's code, or problems with Tomcat, not Jetty. I was wondering whether they could be related to a partially broken iptables configuration (the alternative is a bug in Jetty 6, but I first want to exclude other possible causes). Thanks.

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• How do i send a file with sockets in python?

  - by Jake

  Hi all, I am already familiar with python and socket usage and can send strings of text over these. But how would i go about sending, say, an MP3 file?

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• How the reading from and writing to sockets are synchronized?

  - by Roman

  We create a socket. On one side of the socket we have a "server" and on another side there is a "client". Both, the server and client, can write to and read from the socket. It is what i understand. I do not understand the following things: If a server reads from the socket, does it see in the socket only those stuff which was written to the socket by the client? I mean if server writes something to the socket and than reads from the socket, will it (server) see in the socket the stuff it (server) wrote there? I hope not. Let's consider the following situation. A client write something to the socket and then it writes something new to the socket and then server reads from the socket. What will the server see there? Only the "new" stuff written by the client or both "new" and "old" one? If a client (or server) writes to the socket, can it see if the written information was received by other side? For example out.println("Hello, Server!") will return true it server received this message.

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• Java sockets: can I write a TCP server with one thread?

  - by hmp

  From what I read about Java NIO and non-blocking [Server]SocketChannels, it should be possible to write a TCP server that sustains several connections using only one thread - I'd make a Selector that waits for all relevant channels in the server's loop. Is that right, or am I missing some important detail? What problems can I encounter? (Background: The TCP communication would be for a small multiplayer game, so max. 10-20 simultaneous connections. Messages will be sent about every few seconds.)

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• What to choose API based server or Socket based server for data driven application

  - by Imdad

  I am working on a project which has a Desktop Application for MAC/COCOA, a native application for iPhone another native application in iPad. All the application do almost same thing. The applications are data driven applications. Every communication to server is made via a restful API developed in PHP. When a user logs in a lot of data is fetched from server. And to remain in sync with server pooling is done. As there are lot of data to pool it makes application slower and un-reliable. A possible solution that comes into my mind is to use Socket based server. My question is that will it reasonably improve the performance? And which technology (of sockets) will be good as a server side solution for data driven application? I have heard a lot about Node.js. Please give your suggestions.

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• How would I know if my OS is compromised?

  - by itsols

  I had opened a php folder from a friend's web host. I run it on mine to fix some bugs. Then I tried attaching the code to be emailed and GMAIL stated that the attachment was infected by a virus. Now I'm afraid if my Apache or OS (12.04) is infected. I checked the php files and found a base64 encoded set of code being 'eval'd at the top of each and every php file. Just reversing it (echo with htmlspecialchars) showed some clue that there were sockets in use and something to do with permissions. And also there were two websites referred having .ru extensions. Now I'm afraid if my Ubuntu system is affected or compromised. Any advice please! Here's my second run of rkhunter with the options: sudo rkhunter --check --rwo Warning: The command '/usr/bin/unhide.rb' has been replaced by a script: /usr/bin/unhide.rb: Ruby script, ASCII text Warning: Hidden directory found: /dev/.udev Warning: Hidden file found: /dev/.initramfs: symbolic link to `/run/initramfs'

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• Synchronous HTTP Client with .NET sockets

  - by Ray Wits

  Does anyone know of any open source C# projects or some sample code that implement a synchronous HTTP client using sockets? I'm working on a project where I need a HTTP client using sockets. It can't use WebRequest or WebClient, nor can it use Asynchronous sockets. Don't ask. Also it would ideally be on .NET 2.0, yeah very cutting edge here. I figured the web would have tons of samples for this but suprisingly I couldn't find any. Probably because everyone is fortunate enough to use the built in APIs. If I don't find something I'll have to write it myself, which I don't really want to have to reinvent that wheel.

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• Opening up TCP Sockets in j2ee Webapplication

  - by Gvenez

  Hello, We have to communicate with a C++ component from a J2ee web application and my proposal involved using JMS server to communicate with the C++ component which is located on other machine. However the developer of the C++ component wants me to open up TCP/IP sockets from the webapplication and communicate over XML. My view is that socket programming in web application is error prone and will not scale well since there is a limited amount of sockets that can be opened up. Please let me have your architecture/design preference on using JMS vs TCP/IP sockets. Thank you

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• How to handle Real Time Data from a database perspective?

  - by balexandre

  I have an idea in mind, but it still confuses me the database area. Imagine that I want to show real time data, and using one of the latest browser technologies (web sockets - even using older browsers) it is very easy to show to all observables (user browser) what everyone is doing. Remy Sharp has an example about the simplicity about this. But I still don't get the database part, how would I feed, let's imagine (using Remy game Tron) that I want to save the path for each connected user in a database and if a client wants to see what is going on with a 5 sec delay, he will see that, not only the 5 sec until that moment but the continuation in time ... how can I query a DB like that? SELECT x, y FROM run WHERE time >= DATEADD(second, -5, rundate); is not the recommended path right? and pulling this x in x time ... this is not real data feed correct? If can someone help me understand the Database point of view, I would greatly appreciate.

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• How to match responses from a server with their corresponding requests? [closed]

  - by Deele

  There is a server that responds to requests on a socket. The client has functions to emit requests and functions to handle responses from the server. The problem is that the request sending function and the response handling function are two unrelated functions. Given a server response X, how can I know whether it's a response to request X or some other request Y? I would like to make a construct that would ensure that response X is definitely the answer to request X and also to make a function requestX() that returns response X and not some other response Y. This question is mostly about the general programming approach and not about any specific language construct. Preferably, though, the answer would involve Ruby, TCP sockets, and PHP. My code so far: require 'socket' class TheConnection def initialize(config) @config = config end def send(s) toConsole("--> #{s}") @conn.send "#{s}\n", 0 end def connect() # Connect to the server begin @conn = TCPSocket.open(@config['server'], @config['port']) rescue Interrupt rescue Exception => detail toConsole('Exception: ' + detail.message()) print detail.backtrace.join('\n') retry end end def getSpecificAnswer(input) send "GET #{input}" end def handle_server_input(s) case s.strip when /^Hello. (.*)$/i toConsole "[ Server says hello ]" send "Hello to you too! #{$1}" else toConsole(s) end end def main_loop() while true ready = select([@conn, $stdin], nil, nil, nil) next if !ready for s in ready[0] if s == $stdin then return if $stdin.eof s = $stdin.gets send s elsif s == @conn then return if @conn.eof s = @conn.gets handle_server_input(s) end end end end def toConsole(msg) t = Time.new puts t.strftime("[%H:%M:%S]") + ' ' + msg end end @config = Hash[ 'server'=>'test.server.com', 'port'=>'2020' ] $conn = TheConnection.new(@config) $conn.connect() $conn.getSpecificAnswer('itemsX') begin $conn.main_loop() rescue Interrupt rescue Exception => detail $conn.toConsole('Exception: ' + detail.message()) print detail.backtrace.join('\n') retry end

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• Raw Sockets on Android

  - by Tingo

  I want to create an application that runs on Android and uses Raw Sockets. I see there isn't any raw socket support in the java.net.* or the android.net.* libraries. Are raw sockets possible on Android?

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• squid running out of sockets

  - by drscroogemcduck

  I have a setup where squid sits in front of a java server and acts as a reverse proxy. Recently i've load tested the site and if i fire 100 threads at it each making a request using jmeter i start getting errors in my load test tool like 'no route to host' even though the load test tool and the server are on the same machine. if i run the following command where port 82 is the port my squid server is running on: netstat -ann | grep 82 | wc -l i get 22000 or something and most of them are in TIMED_WAIT. i'm thinking that maybe the huge number of sockets in the TIMED_WAIT state are starving the box of resources.

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• determine if udp socket can be accessed via external client

  - by JohnMerlino

  I don't have access to company firewall server. but supposedly the port 1720 is open on my one ubuntu server. So I want to test it with netcat: sudo nc -ul 1720 The port is listening on the machine ITSELF: sudo netstat -tulpn | grep nc udp 0 0 0.0.0.0:1720 0.0.0.0:* 29477/nc The port is open and in use on the machine ITSELF: lsof -i -n -P | grep 1720 gateway 980 myuser 8u IPv4 187284576 0t0 UDP *:1720 Checked the firewall on current server: sudo ufw allow 1720/udp Skipping adding existing rule Skipping adding existing rule (v6) sudo ufw status verbose | grep 1720 1720/udp ALLOW IN Anywhere 1720/udp ALLOW IN Anywhere (v6) But I try echoing data to it from another computer (I replaced the x's with the real integers): echo "Some data to send" | nc xx.xxx.xx.xxx 1720 But it didn't write anything. So then I try with telnet from the other computer as well: telnet xx.xxx.xx.xxx 1720 Trying xx.xxx.xx.xxx... telnet: connect to address xx.xxx.xx.xxx: Operation timed out telnet: Unable to connect to remote host Although I don't think telnet works with udp sockets. I ran nmap from another computer within the same local network and this is what I got: sudo nmap -v -A -sU -p 1720 xx.xxx.xx.xx Starting Nmap 5.21 ( http://nmap.org ) at 2013-10-31 15:41 EDT NSE: Loaded 36 scripts for scanning. Initiating Ping Scan at 15:41 Scanning xx.xxx.xx.xx [4 ports] Completed Ping Scan at 15:41, 0.10s elapsed (1 total hosts) Initiating Parallel DNS resolution of 1 host. at 15:41 Completed Parallel DNS resolution of 1 host. at 15:41, 0.00s elapsed Initiating UDP Scan at 15:41 Scanning xtremek.com (xx.xxx.xx.xx) [1 port] Completed UDP Scan at 15:41, 0.07s elapsed (1 total ports) Initiating Service scan at 15:41 Initiating OS detection (try #1) against xtremek.com (xx.xxx.xx.xx) Retrying OS detection (try #2) against xtremek.com (xx.xxx.xx.xx) Initiating Traceroute at 15:41 Completed Traceroute at 15:41, 0.01s elapsed NSE: Script scanning xx.xxx.xx.xx. NSE: Script Scanning completed. Nmap scan report for xtremek.com (xx.xxx.xx.xx) Host is up (0.00013s latency). PORT STATE SERVICE VERSION 1720/udp closed unknown Too many fingerprints match this host to give specific OS details Network Distance: 1 hop TRACEROUTE (using port 1720/udp) HOP RTT ADDRESS 1 0.13 ms xtremek.com (xx.xxx.xx.xx) Read data files from: /usr/share/nmap OS and Service detection performed. Please report any incorrect results at http://nmap.org/submit/ . Nmap done: 1 IP address (1 host up) scanned in 2.04 seconds Raw packets sent: 27 (2128B) | Rcvd: 24 (2248B). The only thing I can think of is a firewall or vpn issue. Is there anything else I can check for before requesting that they look at the firewall server again?

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• Threads are facing deadlock in socket program [migrated]

  - by ankur.trapasiya

  I am developing one program in which a user can download a number of files. Now first I am sending the list of files to the user. So from the list user selects one file at a time and provides path where to store that file. In turn it also gives the server the path of file where does it exist. I am following this approach because I want to give stream like experience without file size limitation. Here is my code.. 1) This is server which gets started each time I start my application public class FileServer extends Thread { private ServerSocket socket = null; public FileServer() { try { socket = new ServerSocket(Utils.tcp_port); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } @Override public void run() { try { System.out.println("request received"); new FileThread(socket.accept()).start(); } catch (IOException ex) { ex.printStackTrace(); } } } 2) This thread runs for each client separately and sends the requested file to the user 8kb data at a time. public class FileThread extends Thread { private Socket socket; private String filePath; public String getFilePath() { return filePath; } public void setFilePath(String filePath) { this.filePath = filePath; } public FileThread(Socket socket) { this.socket = socket; System.out.println("server thread" + this.socket.isConnected()); //this.filePath = filePath; } @Override public void run() { // TODO Auto-generated method stub try { ObjectInputStream ois=new ObjectInputStream(socket.getInputStream()); try { //************NOTE filePath=(String) ois.readObject(); } catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } File f = new File(this.filePath); byte[] buf = new byte[8192]; InputStream is = new FileInputStream(f); BufferedInputStream bis = new BufferedInputStream(is); ObjectOutputStream oos = new ObjectOutputStream( socket.getOutputStream()); int c = 0; while ((c = bis.read(buf, 0, buf.length)) > 0) { oos.write(buf, 0, c); oos.flush(); // buf=new byte[8192]; } oos.close(); //socket.shutdownOutput(); // client.shutdownOutput(); System.out.println("stop"); // client.shutdownOutput(); ois.close(); // Thread.sleep(500); is.close(); bis.close(); socket.close(); } catch (IOException ex) { ex.printStackTrace(); } } } NOTE: here filePath represents the path of the file where it exists on the server. The client who is connecting to the server provides this path. I am managing this through sockets and I am successfully receiving this path. 3) FileReceiverThread is responsible for receiving the data from the server and constructing file from this buffer data. public class FileReceiveThread extends Thread { private String fileStorePath; private String sourceFile; private Socket socket = null; public FileReceiveThread(String ip, int port, String fileStorePath, String sourceFile) { this.fileStorePath = fileStorePath; this.sourceFile = sourceFile; try { socket = new Socket(ip, port); System.out.println("receive file thread " + socket.isConnected()); } catch (IOException ex) { ex.printStackTrace(); } } @Override public void run() { try { ObjectOutputStream oos = new ObjectOutputStream( socket.getOutputStream()); oos.writeObject(sourceFile); oos.flush(); // oos.close(); File f = new File(fileStorePath); OutputStream os = new FileOutputStream(f); BufferedOutputStream bos = new BufferedOutputStream(os); byte[] buf = new byte[8192]; int c = 0; //************ NOTE ObjectInputStream ois = new ObjectInputStream( socket.getInputStream()); while ((c = ois.read(buf, 0, buf.length)) > 0) { // ois.read(buf); bos.write(buf, 0, c); bos.flush(); // buf = new byte[8192]; } ois.close(); oos.close(); // os.close(); bos.close(); socket.close(); //Thread.sleep(500); } catch (IOException ex) { ex.printStackTrace(); } } } NOTE : Now the problem that I am facing is at the first time when the file is requested the outcome of the program is same as my expectation. I am able to transmit any size of file at first time. Now when the second file is requested (e.g. I have sent file a,b,c,d to the user and user has received file a successfully and now he is requesting file b) the program faces deadlock at this situation. It is waiting for socket's input stream. I put breakpoint and tried to debug it but it is not going in FileThread's run method second time. I could not find out the mistake here. Basically I am making a LAN Messenger which works on LAN. I am using SWT as UI framework.

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• Postgres - could not create any TCP/IP sockets

  - by Jacka

  I'm running a rails app in development with postgresql 9.3. When I tried to start passenger server today, I got: PG::ConnectionBad - could not connect to server: Connection refused Is the server running on host "localhost" (217.74.65.145) and accepting TCP/IP connections on port 5432? No big deal I thought, that happened before. Restarting postgres always solved the problem. So I ran sudo service postgresql restart and got: * Restarting PostgreSQL 9.3 database server * The PostgreSQL server failed to start. Please check the log output: 2014-06-11 10:32:41 CEST LOG: could not bind IPv4 socket: Cannot assign requested address 2014-06-11 10:32:41 CEST HINT: Is another postmaster already running on port 5432? If not, wait a few seconds and retry. 2014-06-11 10:32:41 CEST WARNING: could not create listen socket for "localhost" 2014-06-11 10:32:41 CEST FATAL: could not create any TCP/IP sockets ...fail! My postgresql.conf points to the defaults: localhost and port 5432. I tried changing the port but the error message is the same (except the port change). Both ps aux | grep postgresql and ps aux | grep postmaster return nothing. EDIT: In postgresql.conf I changed listen_addresses to 127.0.0.1 instead of localhost and it did the trick, server restarted. I also had to edit my applications' db config and point to 127.0.0.1 instead of localhost. However, the question is now, why is localhost considered to be 217.74.65.145 and not 127.0.0.1? That's my /etc/hosts: 127.0.0.1 local 127.0.1.1 jacek-X501A1 127.0.0.1 something.name.non.example.com 127.0.0.1 company.something.name.non.example.com

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