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  • Problem in transfering file from server to client using C sockets

    - by coolrockers2007
    I want to ask, why I cannot transfer file from server to client? When I start to send the file from server, the client side program will have problem. So, I spend some times to check the code, But I still cannot find out the problem Can anyone point out the problem for me? CLIENTFILE.C #include stdio.h #include stdlib.h #include time.h #include netinet/in.h #include fcntl.h #include sys/types.h #include string.h #include stdarg.h #define PORT 5678 #define MLEN 1000 int main(int argc, char *argv []) { int sockfd; int number,message; char outbuff[MLEN],inbuff[MLEN]; //char PWD_buffer[_MAX_PATH]; struct sockaddr_in servaddr; FILE *fp; int numbytes; char buf[2048]; if (argc != 2) fprintf(stderr, "error"); if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) fprintf(stderr, "socket error"); memset(&servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = htons(PORT); if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) fprintf(stderr, "connect error"); if ( (fp = fopen("/home/na/nall9047/write.txt", "w")) == NULL){ perror("fopen"); exit(1); } printf("Still NO PROBLEM!\n"); //Receive file from server while(1){ numbytes = read(sockfd, buf, sizeof(buf)); printf("read %d bytes, ", numbytes); if(numbytes == 0){ printf("\n"); break; } numbytes = fwrite(buf, sizeof(char), numbytes, fp); printf("fwrite %d bytes\n", numbytes); } fclose(fp); close(sockfd); return 0; } SERVERFILE.C #include stdio.h #include fcntl.h #include stdlib.h #include time.h #include string.h #include netinet/in.h #include errno.h #include sys/types.h #include sys/socket.h #includ estdarg.h #define PORT 5678 #define MLEN 1000 int main(int argc, char *argv []) { int listenfd, connfd; int number, message, numbytes; int h, i, j, alen; int nread; struct sockaddr_in servaddr; struct sockaddr_in cliaddr; FILE *in_file, *out_file, *fp; char buf[4096]; listenfd = socket(AF_INET, SOCK_STREAM, 0); if (listenfd < 0) fprintf(stderr,"listen error") ; memset(&servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(PORT); if (bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) fprintf(stderr,"bind error") ; alen = sizeof(struct sockaddr); connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &alen); if (connfd < 0) fprintf(stderr,"error connecting") ; printf("accept one client from %s!\n", inet_ntoa(cliaddr.sin_addr)); fp = fopen ("/home/na/nall9047/read.txt", "r"); // open file stored in server if (fp == NULL) { printf("\nfile NOT exist"); } //Sending file while(!feof(fp)){ numbytes = fread(buf, sizeof(char), sizeof(buf), fp); printf("fread %d bytes, ", numbytes); numbytes = write(connfd, buf, numbytes); printf("Sending %d bytes\n",numbytes); } fclose (fp); close(listenfd); close(connfd); return 0; }

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  • Help with Silverlight Sockets and Message delivery

    - by pixel3cs
    There are 4 months since I stopped developing my Silverlight Multiplayer Chess game. The problem was a bug wich I couldn't reproduce. Sice I got some free time this week I managed to discover the problem and I am now able to reproduce the bug. It seems that if I send 10 messages from client, one after another, with no delay between them, just like in the below example // when I press Enter, the client will 10 messages with no delay between them private void textBox_KeyDown(object sender, KeyEventArgs e) { if (e.Key == Key.Enter && textBox.Text.Length > 0) { for (int i = 0; i < 10; i++) { MessageBuilder mb = new MessageBuilder(); mb.Writer.Write((byte)GameCommands.NewChatMessageInTable); mb.Writer.Write(string.Format("{0}{2}: {1}", ClientVars.PlayerNickname, textBox.Text, i)); SendChatMessageEvent(mb.GetMessage()); //System.Threading.Thread.Sleep(100); } textBox.Text = string.Empty; } } // the method used by client to send a message to server public void SendData(Message message) { if (socket.Connected) { SocketAsyncEventArgs myMsg = new SocketAsyncEventArgs(); myMsg.RemoteEndPoint = socket.RemoteEndPoint; byte[] buffer = message.Buffer; myMsg.SetBuffer(buffer, 0, buffer.Length); socket.SendAsync(myMsg); } else { string err = "Server does not respond. You are disconnected."; socket.Close(); uiContext.Post(this.uiClient.ProcessOnErrorData, err); } } // the method used by server to receive data from client private void OnDataReceived(IAsyncResult async) { ClientSocketPacket client = async.AsyncState as ClientSocketPacket; int count = 0; try { if (client.Socket.Connected) count = client.Socket.EndReceive(async); // THE PROBLEM IS HERE // IF SERVER WAS RECEIVE ALL MESSAGES SEPARATELY, ONE BY ONE, THE COUNT // WAS ALWAYS 15, BUT BECAUSE THE SERVER RECEIVE 3 MESSAGES IN 1, THE COUNT // IS SOMETIME 45 } catch { HandleException(client); } client.MessageStream.Write(client.Buffer, 0, count); Message message; while (client.MessageStream.Read(out message)) { message.Tag = client; ThreadPool.QueueUserWorkItem(new WaitCallback(this.processingThreadEvent.ServerGotData), message); totalReceivedBytes += message.Buffer.Length; } try { if (client.Socket.Connected) client.Socket.BeginReceive(client.Buffer, 0, client.Buffer.Length, 0, new AsyncCallback(OnDataReceived), client); } catch { HandleException(client); } } there are sent only 3 big messages, and every big message contain 3 or 4 small messages. This is not the behavior I want. If I put a 100 milliseconds delay between message delivery, everything is work fine, but in a real world scenario users can send messages to server even at 1 millisecond between them. Are there any settings to be done in order to make the client send only one message at a time, or Even if I receive 3 messages in 1, are they full messages all the time (I dont't want to receive 2.5 messages in one big message) ? because if they are, I can read them and treat this new situation

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  • Python and C++ Sockets converting packet data

    - by yeus
    First of all, to clarify my goal: There exist two programs written in C in our laboratory. I am working on a Proxy Server (bidirectional) for them (which will also mainpulate the data). And I want to write that proxy server in Python. It is important to know that I know close to nothing about these two programs, I only know the definition file of the packets. Now: assuming a packet definition in one of the C++ programs reads like this: unsigned char Packet[0x32]; // Packet[Length] int z=0; Packet[0]=0x00; // Spare Packet[1]=0x32; // Length Packet[2]=0x01; // Source Packet[3]=0x02; // Destination Packet[4]=0x01; // ID Packet[5]=0x00; // Spare for(z=0;z<=24;z+=8) { Packet[9-z/8]=((int)(720000+armcontrolpacket->dof0_rot*1000)/(int)pow((double)2,(double)z)); Packet[13-z/8]=((int)(720000+armcontrolpacket->dof0_speed*1000)/(int)pow((double)2,(double)z)); Packet[17-z/8]=((int)(720000+armcontrolpacket->dof1_rot*1000)/(int)pow((double)2,(double)z)); Packet[21-z/8]=((int)(720000+armcontrolpacket->dof1_speed*1000)/(int)pow((double)2,(double)z)); Packet[25-z/8]=((int)(720000+armcontrolpacket->dof2_rot*1000)/(int)pow((double)2,(double)z)); Packet[29-z/8]=((int)(720000+armcontrolpacket->dof2_speed*1000)/(int)pow((double)2,(double)z)); Packet[33-z/8]=((int)(720000+armcontrolpacket->dof3_rot*1000)/(int)pow((double)2,(double)z)); Packet[37-z/8]=((int)(720000+armcontrolpacket->dof3_speed*1000)/(int)pow((double)2,(double)z)); Packet[41-z/8]=((int)(720000+armcontrolpacket->dof4_rot*1000)/(int)pow((double)2,(double)z)); Packet[45-z/8]=((int)(720000+armcontrolpacket->dof4_speed*1000)/(int)pow((double)2,(double)z)); Packet[49-z/8]=((int)armcontrolpacket->timestamp/(int)pow(2.0,(double)z)); } if(SendPacket(sock,(char*)&Packet,sizeof(Packet))) return 1; return 0; What would be the easiest way to receive that data, convert it into a readable python format, manipulate them and send them forward to the receiver?

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  • Data not synchornizing java sockets

    - by Droid_Interceptor
    I am writing a auction server and client and using a class called BidHandler to deal with the bids another class AuctionItem to deal with the items for auction. The main problem I am having is little synchroization problem. Screen output of client server as can see from the image at 1st it takes the new bid and changes the value of the time to it, but when one the user enters 1.0 the item seems to be changed to that. But later on when the bid changes again to 15.0 it seems to stay at that price. Is there any reason for that. I have included my code below. Sorry if didnt explain this well. This is the auction client import java.io.*; import java.net.*; public class AuctionClient { private AuctionGui gui; private Socket socket; private DataInputStream dataIn; private DataOutputStream dataOut; //Auction Client constructor String name used as identifier for each client to allow server to pick the winning bidder public AuctionClient(String name,String server, int port) { gui = new AuctionGui("Bidomatic 5000"); gui.input.addKeyListener (new EnterListener(this,gui)); gui.addWindowListener(new ExitListener(this)); try { socket = new Socket(server, port); dataIn = new DataInputStream(socket.getInputStream()); dataOut = new DataOutputStream(socket.getOutputStream()); dataOut.writeUTF(name); while (true) { gui.output.append("\n"+dataIn.readUTF()); } } catch (Exception e) { e.printStackTrace(); } } public void sentBid(String bid) { try { dataOut.writeUTF(bid); } catch(IOException e) { e.printStackTrace(); } } public void disconnect() { try { socket.close(); } catch(IOException e) { e.printStackTrace(); } } public static void main (String args[]) throws IOException { if(args.length!=3) { throw new RuntimeException ("Syntax: java AuctionClient <name> <serverhost> <port>"); } int port = Integer.parseInt(args[2]); AuctionClient a = new AuctionClient(args[0],args[1],port); } } The Auction Server import java.io.*; import java.net.*; import java.util.*; public class AuctionServer { public AuctionServer(int port) throws IOException { ServerSocket server = new ServerSocket(port); while(true) { Socket client = server.accept(); DataInputStream in = new DataInputStream(client.getInputStream()); String name = in.readUTF(); System.out.println("New client "+name+" from " +client.getInetAddress()); BidHandler b = new BidHandler (name, client); b.start(); } } public static void main(String args[]) throws IOException { if(args.length != 1) throw new RuntimeException("Syntax: java AuctionServer <port>"); new AuctionServer(Integer.parseInt(args[0])); } } The BidHandler import java.net.*; import java.io.*; import java.util.*; import java.lang.Float; public class BidHandler extends Thread { Socket socket; DataInputStream in; DataOutputStream out; String name; float currentBid = 0.0f; AuctionItem paper = new AuctionItem(" News Paper ", " Free newspaper from 1990 ", 1.0f, false); protected static Vector handlers = new Vector(); public BidHandler(String name, Socket socket) throws IOException { this.name = name; this.socket = socket; in = new DataInputStream (new BufferedInputStream (socket.getInputStream())); out = new DataOutputStream(new BufferedOutputStream(socket.getOutputStream())); } public synchronized void run() { try { broadcast("New bidder has entered the room"); handlers.addElement(this); while(true) { broadcast(paper.getName() + paper.getDescription()+" for sale at: " +paper.getPrice()); while(paper.getStatus() == false) { String message = in.readUTF(); currentBid = Float.parseFloat(message); broadcast("Bidder entered " +currentBid); if(currentBid > paper.getPrice()) { paper.setPrice(currentBid); broadcast("New Higgest Bid is "+paper.getPrice()); } else if(currentBid < paper.getPrice()) { broadcast("Higgest Bid is "+paper.getPrice()); } else if(currentBid == paper.getPrice()) { broadcast("Higgest Bid is "+paper.getPrice()); } } } } catch(IOException ex) { System.out.println("-- Connection to user lost."); } finally { handlers.removeElement(this); broadcast(name+" left"); try { socket.close(); } catch(IOException ex) { System.out.println("-- Socket to user already closed ?"); } } } protected static void broadcast (String message) { synchronized(handlers) { Enumeration e = handlers.elements(); while(e.hasMoreElements()) { BidHandler handler = (BidHandler) e.nextElement(); try { handler.out.writeUTF(message); handler.out.flush(); } catch(IOException ex) { handler = null; } } } } } The AuctionItem Class class AuctionItem { String itemName; String itemDescription; float itemPrice; boolean itemStatus; //Create a new auction item with name, description, price and status public AuctionItem(String name, String description, float price, boolean status) { itemName = name; itemDescription = description; itemPrice = price; itemStatus = status; } //return the price of the item. public synchronized float getPrice() { return itemPrice; } //Set the price of the item. public synchronized void setPrice(float newPrice) { itemPrice = newPrice; } //Get the status of the item public synchronized boolean getStatus() { return itemStatus; } //Set the status of the item public synchronized void setStatus(boolean newStatus) { itemStatus = newStatus; } //Get the name of the item public String getName() { return itemName; } //Get the description of the item public String getDescription() { return itemDescription; } } There is also simple GUI to go with this that seems to be working fine. If anyone wants it will include the GUI code.

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  • Remotely connecting two non-local computers with sockets

    - by Velizar Hristov
    This question seems like something very obvious to ask, and yet I spent more than an hour trying to find an answer. First I host and wait for someone to connect. Then, from another instance of the application, I try to connect with a socket - for the constructor, I use InetAddress, port. The port is always right, and everything works if I use "localhost" for the address. However, if I type my IP, I get an IOException. I even sent the application to someone else, gave him my IP, and it didn't work. The aim of the application is to connect two computers. It's in Java. Here is the relevant code. Server: ServerSocket serverSocket = new ServerSocket(port); Socket clientSocket = serverSocket.accept(); Client: InetAddress a = InetAddress.getByName(ip); Socket s = new Socket(a, port); I don't get past that. Obviously, the values of int port and String ip are taken from text fields. Edit: the purpose of my application is to connect two non-local computers.

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  • Should I close sockets from both ends?

    - by Roman
    I have the following problem. My client program monitor for availability of server in the local network (using Bonjour, but it does not rally mater). As soon as a server is "noticed" by the client application, the client tries to create a socket: Socket(serverIP,serverPort);. At some point the client can loose the server (Bonjour says that server is not visible in the network anymore). So, the client decide to close the socket, because it is not valid anymore. At some moment the server appears again. So, the client tries to create a new socket associated with this server. But! The server can refuse to create this socket since it (server) has already a socket associated with the client IP and client port. It happens because the socket was closed by the client, not by the server. Can it happen? And if it is the case, how this problem can be solved? Well, I understand that it is unlikely that the client will try to connect to the server from the same port (client port), since client selects its ports randomly. But it still can happen (just by chance). Right?

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  • multiple clients - one server connection with sockets tcp/ip c# .net

    - by jagse
    Hello guys, I need to develop a client server system where I can have multiple clients communicating with one server at the same time. I want to communicate xml serialized objects and also need to send and receive other commands to invoke methods. Now, I am just starting with socket programming in C# and .Net and found that the asynchronous I/O is the way to go so that the methods dont block the execution of code. Also there are many examples of how to make a simple client server system. So I have a basic understanding of how that works. Anyway, what still is not clear to me is how I can set up a server which can manage connections to multiple clients? Can I just create a new socket per connection and then store those in some kind of list? Do I need some kind of multiplexing to achieve this? Do I have to listen at multiple ports? What`s the best way here? And the other thing is if I need to develop my own protocol to differentiate between what I am actually sending over the network -- xml serialized object or a command which might be just a string encoded in ascII or something. Or would I develop my own protocol just to send these commands? Any kind of help is apreciated! If someone knows a good book which covers this sort of stuff, let me know. Cheers I forgot to mention that some of my clients which are supposed to communicate with my server will be pda and I therefore use the compact framework... So this might bring in some restrictions...

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  • sending and receiving with sockets in java?

    - by Darksole
    I am working on sending and receiving from clients and servers in java, and am stumped at the moment. the client socket is to contact a server at “localhost” port 4321. The client will receive a string from the server and alternate spelling the contents of this string with the server. For example, given the string “Bye Bye”, the client (which always begins sending the first letter) sends “B”, receives “y”, sends “e”, receives “ ”, sends “B”, receives “y”, sends “e”, and receives “done!”, which is the string that either client or server will send after the last letter from the original string is received. After “done!” is transmitted, both client and server close their communications. How would i go about getting the first string and then going back and forth sending and reciving letters that make the string, and when finished either send or get done!? import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintWriter; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner; public class Program2 { public static void goClient() throws UnknownHostException, IOException{ String server = "localhost"; int port = 4321; Socket socket = new Socket(server, port); InputStream inStream = socket.getInputStream(); OutputStream outStream = socket.getOutputStream(); Scanner in = new Scanner(inStream); PrintWriter out = new PrintWriter(outStream, true); String rec = ""; if(in.hasNext()){ rec = in.nextLine(); } char[] array = new char[rec.length()]; for(int i = 0; i < rec.length(); i++){ array[i] = rec.charAt(i); } while(in.hasNext()){ for(int x = 0; x < array.length + 1; x+=2){ String str = in.nextLine(); str = Character.toString(array[x]); out.println(str); } in.close(); socket.close(); } } }

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  • How to implement bridging/NAT on linux? [closed]

    - by mikepurvis
    What I have is a network topology which looks like this: ------ PC --- IP Camera The PC has two ethernet interfaces, and is hosting a small webserver providing some auxiliary data. The issue is that the server on the PC runs on port 80, and the IP Camera is also running on port 80. Currently, we are bridging them, so that the PC's server is accessible at 192.168.0.2 and the camera at 192.168.0.3. However, what I'm trying to explore is the feasibility of using the PC to expose them both on the PC's IP, ideally both on port 80. Can this be done with regular sockets, or will it be necessary to use raw sockets?

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  • Sockets: Transport endpoint is not connected on send

    - by TheoretiCAL
    I'm trying to learn socket programming from http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html and am attempting to build a SOCK_STREAM client/server. My client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #define SERVERPORT "4951" // the port users will be connecting to int main(int argc, char *argv[]) { int sockfd; struct addrinfo hints, *servinfo, *p; int rv; int numbytes; if (argc != 3) { fprintf(stderr,"usage: talker hostname message\n"); exit(1); } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return 1; } // loop through all the results and make a socket for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("talker: socket"); continue; if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) { close(sockfd); perror("client: connect"); continue; } } break; } if (p == NULL) { fprintf(stderr, "talker: failed to bind socket\n"); return 2; } if ((numbytes = send(sockfd, argv[2], strlen(argv[2]), 0) == -1)) { perror("talker: send"); exit(1); } freeaddrinfo(servinfo); printf("talker: sent %d bytes to %s\n", numbytes, argv[1]); close(sockfd); return 0; } Server: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #define MYPORT "4951" // the port users will be connecting to #define MAXBUFLEN 100 static int backlog = 10; // get sockaddr, IPv4 or IPv6: void *get_in_addr(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); } return &(((struct sockaddr_in6*)sa)->sin6_addr); } int main(void) { int sockfd; struct addrinfo hints, *servinfo, *p; int rv; int numbytes; int new_fd; socklen_t addr_size; struct sockaddr_storage their_addr; char buf[MAXBUFLEN]; char s[INET6_ADDRSTRLEN]; memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4 hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // use my IP if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return 1; } // loop through all the results and bind to the first we can for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("listener: socket"); continue; } int yes=1; // lose the pesky "Address already in use" error message if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) { perror("setsockopt"); exit(1); } if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { close(sockfd); perror("listener: bind"); continue; } if (listen(sockfd,backlog) == -1){ close(sockfd); perror("listener:listen"); continue; } break; } if (p == NULL) { fprintf(stderr, "listener: failed to bind socket\n"); return 2; } freeaddrinfo(servinfo); printf("listener: waiting to recv..\n"); while(1){ addr_size = sizeof their_addr; if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_size))==-1){ perror("accept"); exit(1); } if ((numbytes = recv(new_fd, buf, MAXBUFLEN-1 , 0) == -1)) { perror("recv"); exit(1); } printf("listener: got packet from %s\n", inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s)); printf("listener: packet is %d bytes long\n", numbytes); buf[numbytes] = '\0'; printf("listener: packet contains \"%s\"\n", buf); close(sockfd); } return 0; } Upon executing the client, I get " send: Transport endpoint is not connected" and I'm not sure where I went wrong. Thanks.

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  • reading partially from sockets

    - by nomad.alien
    I'm having a little test program that sends a lot of udp packets between client-server-client (ping/pong test). The packets are fixed size on each run(last run is max allowable size of udp packet) I'm filling the packets with random data except for the beginning of each packet that contains the packet number. So I'm only interested to see if I receive all the packets back at the client. I'm using sendto() and recvfrom() and I only read the sizeof(packet_number) (which in this case is an int). What happens to the rest of the data? Does it end up in fairyland (gets discarded)? or does the new packet that arrives gets appended to this "old" data? (using linux)

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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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  • Current stock price by using sockets in java

    - by user2976396
    My program is to find the current stock price of a symbol ..this is the code which i m using `String yahoo = "finance.yahoo.com" ; final int httpd = 80; Socket sock = new Socket(yahoo,httpd); PrintWriter out = new PrintWriter( sock.getOutputStream(), true ); BufferedReader in =new BufferedReader(new InputStreamReader( sock.getInputStream() ) ); out.println( "GET http://finance.yahoo.com/q?s=ibm&f=1l HTTP/1.0\r\n\r\n " ); out.println(""); out.flush();` I am just getting the output as ibm .Can anyone please suggest how to get the price.

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  • Sending Data as Instances using Python Sockets

    - by Alice
    I'm working on the networking part of a 2 player game (similar to tetris), and I'm trying to pass the game grid from client to server and vice versa. However, when I tried using send(grid) I get a TypeError: send() argument 1 must be string or read-only buffer, not instance. Is there anyway to circumvent this, or do I have to convert my grid instance into a string and then interpret it from the other side? Thanks in advance!

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  • Sockets: I/O Error 32

    - by Genesis
    Could someone please explain what an I/O Error 32 refers to in the context of a network socket? I have a multithreaded Socks5 server written using Poco SocketReactors and am getting this error when the server load reaches a certain point. The exception is thrown within my onReadable handlers at the same time across all threads which have connections associated with them. The only other thing I am doing within those threads is std::cout but I am not sure if this is a potential cause.

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  • gevent, sockets and syncronisation

    - by schlamar
    I have multiple greenlets sending on a common socket. Is it guaranteed that each package sent via socket.sendall is well separated or do I have to acquire a lock before each call to sendall. So I want to prevent the following scenario: g1 sends ABCD g2 sends 1234 received data is mixed up, for example AB1234CD expected is either ABCD1234 or 1234ABCD Update After a look at the sourcecode I think this scenario cannot happen. But I have to use a lock because g1 or g2 can crash on the sendall. Can someone confirm this?

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  • Sending Images over Sockets in C

    - by Takkun
    I'm trying to send an image file through a TCP socket in C, but the image isn't being reassembled correctly on the server side. I was wondering if anyone can point out the mistake? I know that the server is receiving the correct file size and it constructs a file of that size, but it isn't an image file. Client //Get Picture Size printf("Getting Picture Size\n"); FILE *picture; picture = fopen(argv[1], "r"); int size; fseek(picture, 0, SEEK_END); size = ftell(picture); //Send Picture Size printf("Sending Picture Size\n"); write(sock, &size, sizeof(size)); //Send Picture as Byte Array printf("Sending Picture as Byte Array\n"); char send_buffer[size]; while(!feof(picture)) { fread(send_buffer, 1, sizeof(send_buffer), picture); write(sock, send_buffer, sizeof(send_buffer)); bzero(send_buffer, sizeof(send_buffer)); } Server //Read Picture Size printf("Reading Picture Size\n"); int size; read(new_sock, &size, sizeof(1)); //Read Picture Byte Array printf("Reading Picture Byte Array\n"); char p_array[size]; read(new_sock, p_array, size); //Convert it Back into Picture printf("Converting Byte Array to Picture\n"); FILE *image; image = fopen("c1.png", "w"); fwrite(p_array, 1, sizeof(p_array), image); fclose(image);

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  • How the clients (client sockets) are identified?

    - by Roman
    To my understanding by serverSocket = new ServerSocket(portNumber) we create an object which potentially can "listen" to the indicated port. By clientSocket = serverSocket.accept() we force the server socket to "listen" to its port and to "accept" a connection from any client which tries to connect to the server through the port associated with the server. When I say "client tries to connect to the server" I mean that client program executes "nameSocket = new Socket(serverIP,serverPort)". If client is trying to connect to the server, the server "accepts" this client (i.e. creates a "client socket" associated with this client). If a new client tries to connect to the server, the server creates another client socket (associated with the new client). But how the server knows if it is a "new" client or an "old" one which has already its socket? Or, in other words, how the clients are identified? By their IP? By their IP and port? By some "signatures"? What happens if an "old" client tries to use Socket(serverIP,serverIP) again? Will server create the second socket associated with this client?

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  • Handling large numbers of sockets with .NET

    - by Dreaddan
    I'm looking at writing a application that need to be able to handle in the region of 200 connections / sec and was wondering if C# and .NET will handle this or if I need to really be looking at C++ to do this? It looks like SocketAsyncEventArgs may be the way to go but thought id check before I plough in to it. Each transaction should only last less than a second but could take up to 15 seconds each if that makes any difference.

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  • Marshal.StringToCoTaskMemAnsi converting non-Latin characters when sending raw data to a printer

    - by rem
    For sending raw data to a thermal DATAMAX printer I'm using RawPrinterHelper class from this Microsoft KB article. When a string sent to printer contains only Latin characters, everything is OK. But non-Latin, in my case Russian characters in a string, are not printed correct. I think the problem is in using Marshal.StringToCoTaskMemAnsi method for converting the string: public static bool SendStringToPrinter(string szPrinterName, string szString) { IntPtr pBytes; Int32 dwCount; // How many characters are in the string? dwCount = szString.Length; // Assume that the printer is expecting ANSI text, and then convert // the string to ANSI text. pBytes = Marshal.StringToCoTaskMemAnsi(szString); // Send the converted ANSI string to the printer. SendBytesToPrinter(szPrinterName, pBytes, dwCount); Marshal.FreeCoTaskMem(pBytes); return true; } Just to note, Russian characters in the string are put in hex format, like "\x83", but nevertheless the method doesn't put this hex value in unmanaged memory as it is, but converts it, I think, according with ANSI code page to a character and then printer can not read it correctly. If I try to compose a file, using Hex editor and put correct hex values in place of non-Latin characters and then send the file to a printer using another method from the same class SendFileToPrinter, everything, including Russian characters is printed correctly. How in this case the problem with sending string, containing non-Latin characters, could be solved?

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  • Raw types and subtyping

    - by Dmitrii
    We have generic class SomeClass<T>{ } We can write the line: SomeClass s= new SomeClass<String>(); It's ok, because raw type is supertype for generic type. But SomeClass<String> s= new SomeClass(); is correct to. Why is it correct? I thought that type erasure was before type checking, but it's wrong. From Hacker's Guide to Javac When the Java compiler is invoked with default compile policy it performs the following passes: parse: Reads a set of *.java source files and maps the resulting token sequence into AST-Nodes. enter: Enters symbols for the definitions into the symbol table. process annotations: If Requested, processes annotations found in the specified compilation units. attribute: Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. flow: Performs data ow analysis on the trees from the previous step. This includes checks for assignments and reachability. desugar: Rewrites the AST and translates away some syntactic sugar. generate: Generates Source Files or Class Files. Generic is syntax sugar, hence type erasure invoked at 6 pass, after type checking, which invoked at 4 pass. I'm confused.

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  • Why does BeginReceiveFrom never time out?

    - by James Hugard
    I am writing an asynchronous Ping using Raw Sockets in F#, to enable parallel requests using as few threads as possible ("System.Net.NetworkInformation.Ping" appears to use one thread per request, but have not tested this... also am interested in using F# async workflows). The synchronous version below correctly times out when the target host does not exist/respond, but the asynchronous version hangs. Both work when the host does respond... Any ideas? (note: the process must run as Admin for this code to work) This throws a timeout: let result = Ping.Ping ( IPAddress.Parse( "192.168.33.22" ), 1000 ) However, this hangs: let result = Ping.PingAsync ( IPAddress.Parse( "192.168.33.22" ), 1000 ) |> Async.RunSynchronously Here's the code... module Ping open System open System.Net open System.Net.Sockets open System.Threading //---- ICMP Packet Classes type IcmpMessage (t : byte) = let mutable m_type = t let mutable m_code = 0uy let mutable m_checksum = 0us member this.Type with get() = m_type member this.Code with get() = m_code member this.Checksum = m_checksum abstract Bytes : byte array default this.Bytes with get() = [| m_type m_code byte(m_checksum) byte(m_checksum >>> 8) |] member this.GetChecksum() = let mutable sum = 0ul let bytes = this.Bytes let mutable i = 0 // Sum up uint16s while i < bytes.Length - 1 do sum <- sum + uint32(BitConverter.ToUInt16( bytes, i )) i <- i + 2 // Add in last byte, if an odd size buffer if i <> bytes.Length then sum <- sum + uint32(bytes.[i]) // Shuffle the bits sum <- (sum >>> 16) + (sum &&& 0xFFFFul) sum <- sum + (sum >>> 16) sum <- ~~~sum uint16(sum) member this.UpdateChecksum() = m_checksum <- this.GetChecksum() type InformationMessage (t : byte) = inherit IcmpMessage(t) let mutable m_identifier = 0us let mutable m_sequenceNumber = 0us member this.Identifier = m_identifier member this.SequenceNumber = m_sequenceNumber override this.Bytes with get() = Array.append (base.Bytes) [| byte(m_identifier) byte(m_identifier >>> 8) byte(m_sequenceNumber) byte(m_sequenceNumber >>> 8) |] type EchoMessage() = inherit InformationMessage( 8uy ) let mutable m_data = Array.create 32 32uy do base.UpdateChecksum() member this.Data with get() = m_data and set(d) = m_data <- d this.UpdateChecksum() override this.Bytes with get() = Array.append (base.Bytes) (this.Data) //---- Synchronous Ping let Ping (host : IPAddress, timeout : int ) = let mutable ep = new IPEndPoint( host, 0 ) let socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout ) let packet = EchoMessage() let mutable buffer = packet.Bytes try if socket.SendTo( buffer, ep ) <= 0 then raise (SocketException()) buffer <- Array.create (buffer.Length + 20) 0uy let mutable epr = ep :> EndPoint if socket.ReceiveFrom( buffer, &epr ) <= 0 then raise (SocketException()) finally socket.Close() buffer //---- Entensions to the F# Async class to allow up to 5 paramters (not just 3) type Async with static member FromBeginEnd(arg1,arg2,arg3,arg4,beginAction,endAction,?cancelAction): Async<'T> = Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,iar,state)), endAction, ?cancelAction=cancelAction) static member FromBeginEnd(arg1,arg2,arg3,arg4,arg5,beginAction,endAction,?cancelAction): Async<'T> = Async.FromBeginEnd((fun (iar,state) -> beginAction(arg1,arg2,arg3,arg4,arg5,iar,state)), endAction, ?cancelAction=cancelAction) //---- Extensions to the Socket class to provide async SendTo and ReceiveFrom type System.Net.Sockets.Socket with member this.AsyncSendTo( buffer, offset, size, socketFlags, remoteEP ) = Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP, this.BeginSendTo, this.EndSendTo ) member this.AsyncReceiveFrom( buffer, offset, size, socketFlags, remoteEP ) = Async.FromBeginEnd( buffer, offset, size, socketFlags, remoteEP, this.BeginReceiveFrom, (fun asyncResult -> this.EndReceiveFrom(asyncResult, remoteEP) ) ) //---- Asynchronous Ping let PingAsync (host : IPAddress, timeout : int ) = async { let ep = IPEndPoint( host, 0 ) use socket = new Socket( AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.Icmp ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.SendTimeout, timeout ) socket.SetSocketOption( SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout ) let packet = EchoMessage() let outbuffer = packet.Bytes try let! result = socket.AsyncSendTo( outbuffer, 0, outbuffer.Length, SocketFlags.None, ep ) if result <= 0 then raise (SocketException()) let epr = ref (ep :> EndPoint) let inbuffer = Array.create (outbuffer.Length + 256) 0uy let! result = socket.AsyncReceiveFrom( inbuffer, 0, inbuffer.Length, SocketFlags.None, epr ) if result <= 0 then raise (SocketException()) return inbuffer finally socket.Close() }

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  • Raw XML Push from input stream captures only the first line of XML

    - by pqsk
    I'm trying to read XML that is being pushed to my java app. I originally had this in my glassfish server working. The working code in glassfish is as follows: public class XMLPush implements Serializable { public void processXML() { StringBuilder sb = new StringBuilder(); BufferedReader br = null; try { br = ((HttpServletRequest)FacesContext.getCurrentInstance().getExternalContext().getRequest()).getReader (); String s = null; while((s = br.readLine ()) != null) { sb.append ( s ); } //other code to process xml ........... ............................. }catch(Exception ex) { XMLCreator.exceptionOutput ( "processXML","Exception",ex); } .... ..... }//processXML }//class It works perfect, but my client is unable to have glassfish on their server. I tried grabbing the raw xml from php, but I couldn't get it to work. I decided to open up a socket and listen for the xml push manually. Here is my code for receiving the push: public class ListenerService extends Thread { private BufferedReader reader = null; private String line; public ListenerService ( Socket connection )thows Exception { this.reader = new BufferedReader ( new InputStreamReader ( connection.getInputStream () ) ); this.line = null; }//ListenerService @Override public void run () { try { while ( (this.line = this.reader.readLine ()) != null) { System.out.println ( this.line ); ........ }//while } System.out.println ( ex.toString () ); } } catch ( Exception ex ) { ... }//catch }//run I haven't done much socket programing, but from what I read for the past week is that passing the xml into a string is bad. What am I doing wrong and why is it that in glassfish server it works, and when I just open a socket myself it doesn't? this is all that I receive from the push: PUT /?XML_EXPORT_REASON=ResponseLoop&TIMESTAMP=1292559547 HTTP/1.1 Host: ************************ Accept: */* Content-Length: 470346 Expect: 100-continue <?xml version="1.0" encoding="UTF-8" ?> Where did the xml go? Is it because I am placing it in a string? I just need to grab the xml and save it into a file and then process it. Everything else works, but this.Any help would be greatly appreciated.

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  • Help understanding linux/tcp.h

    - by Chris
    I'm learning to use raw sockets, and im trying to prase out the tcp header data, but i can't seem to figure out what res1, ece, and cwr are. Through my networking book and google i know what the rest stand for, but can't seem to find anything on those three. Below is the tcphdr struct in my includes area. Ive commented the parts a bit as i was figureing out what they stood for. struct tcphdr { __be16 source; __be16 dest; __be32 seq; __be32 ack_seq; #if defined(__LITTLE_ENDIAN_BITFIELD) _u16 res1:4, doff:4,//tcp header length fin:1,//final syn:1,//synchronization rst:1,//reset psh:1,//push ack:1,//ack urg:1,// urge ece:1, cwr:1; #elif defined(_BIG_ENDIAN_BITFIELD) __u16 doff:4,//tcp header length res1:4, cwr:1, ece:1, urg:1,//urge ack:1,//ack psh:1,//push rst:1,//reset syn:1,//synchronization fin:1;//final #else #error "Adjust your defines" #endif __be16 window; __sum16 check; __be16 urg_ptr; };

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