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• Should I continue to pursue programming based on my experience?

  - by El Be

  The reason I ask this question is because I am not sure my troubles come from a lack of confidence, or something much deeper like lack of passion. I'm hoping experienced programmers and developers can help identify the cause of my troubles. To be brief my undergraduate major was in Computer Science, but in a small school and I had the highest gpa in my year in computer science. The first time I ever programmed was once in the 5th grade (using logo) and when I was a freshman in college. I enjoyed programming when I was in school. Then I did an internships where I was expected to produce image processing software and program microchips. I was unsuccessful and produced little results and I hated the job, because I had to figure out everything for myself, did not have any help, and there was a lot of pressure to produce results. Although I tried I could not figure out what to do and was stuck all the time and made me dislike the job. When the internship ended I went to a PhD program for computer science at a prestigious computer science school. I had a very hard time with the course, met people who have been programming since they were 6 and made plenty of applications in their spare time (which I never did, although I tried). I even met many sophomores who understood more than I did. The combination of this and other things have made me feel that programming is not for me, but sometimes I consider a career in programming. I still consider programming as a career because of the career potential (not only just because of money). Based on my experience do you believe my confidence has just been shaken and I should continue to prepare for a programming career, or do you see a lack of passion and it would make it tough to continue programming. thank you for reading and for your advice Thank you for everyone's advice so far! Also: I dropped out of the ph.D program for computer science and switched to a master's in computer graphics. Its more applied, but I still find it hard to be motivated (due to either lack of confidence or passion), but since programming is such a big field I am looking for that niche area that I feel good programming in.

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• NetworkStream.Read delay .Net

  - by Gilbes

  I have a class that inherits from TcpClient. In that class I have a method to process responses. In that method I call I get the NetworkStream with MyBase.GetStream and call Read on it. This works fine, excpet the first call to read blocks too long. And by too long I mean that the socket has recieved plenty of data, but won't read it until some arbitrary limit is reached. I can see that it has recieved plenty of data using the packet sniffer WireShark. I have set the recieve buffer to small amounts, and very small amounts (like just a few bytes) to no avail. I have done the same with the buffer byte array I pass to the read method, and it still delays. Or to put it another way. I am download 600k. The download takes 5 seconds (at a little over 100k/second connection to the server which makes sense). The initial Read call takes 2-3 seconds and tells me only 256 bytes are availble (256 is the Recieve buffer and the size of the array I read in to). Then magically, the other few hundred thousand bytes can be read in 256 byte chunks in only a few process ticks each. Using a packet sniffer, I know that during those initial 2-3 seconds, the socket has recieved much more than just 256 bytes. My connection wasn't .25k/second for 3 seconds and then 400k for 2 seconds. How do I get the bytes from a socket as they come in?

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• Boost ASIO Headache

  - by bobber205

  Man... thought using ASIO in Boost was going to be easy and intuitive. :P I am starting to get it finally but I am having some trouble. Here's a snippet. I am having several compiler errors on the async_accept line. What am I doing wrong? :P I've based my code off of this page: http://www.boost.org/doc/libs/1_43_0/doc/html/boost_asio/tutorial/tutdaytime3/src.html bool TestSocket::StartListening(int port) { bool didStart = false; if (!this->listening) { //try to listen acceptor = new tcp::acceptor(this->myService, tcp::endpoint(tcp::v4(), port)); 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; } void TestSocket::NewConnection(tcp::socket* s, const boost::system::error_code& error) { }

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• How can I build a wrapper to wait for listening on a port?

  - by BillyBBone

  Hi, I am looking for a way of programmatically testing a script written with the asyncore Python module. My test consists of launching the script in question -- if a TCP listen socket is opened, the test passes. Otherwise, if the script dies before getting to that point, the test fails. The purpose of this is knowing if a nightly build works (at least up to a point) or not. I was thinking the best way to test would be to launch the script in some kind of sandbox wrapper which waits for a socket request. I don't care about actually listening for anything on that port, just intercepting the request and using that as an indication that my test passed. I think it would be preferable to intercept the open socket request, rather than polling at set intervals (I hate polling!). But I'm a bit out of my depths as far as how exactly to do this. Can I do this with a shell script? Or perhaps I need to override the asyncore module at the Python level? Thanks in advance, - B

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• POSIX Sockets: How to detect Ctrl-C sent over Telnet?

  - by ogott

  Short Question What's the right way to handle a Ctrl-C event sent over Telnet on the server side? Long Question After calling recv() on a socket, I'd like to handle some situations appropriately. One of them is to return a certain error code when Ctrl-C was received. What's the correct way to detect this? The following works, but it just doesn't seem right: size_t recv_count; static char ctrl_c[5] = {0xff, 0xf4, 0xff, 0xfd, 0x06}; recv_count = recv(socket, buffer, buffer_size, 0); if (recv_count == sizeof(ctrl_c) && memcmp(buffer, ctrl_c, sizeof(ctrl_c) == 0) { return CTRL_C_RECEIVED; } I found a comment on Ctrl-C in a side-note in this UNIX Socket FAQ: [...] (by the way, out-of-band is often used for that ctrl-C, too). As I understand, receiving out-of-band data is done using recv() with a certain flag as the last parameter. But when I'm waiting for data using recv() as I do in the code above, I can't read out-of-band data at the same time. Apart from that, I'm getting something using recv() without that oob-flag.

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• How can we improve overall Programmer Education & Training?

  - by crosenblum

  Last week, I was just viewing this amazing interview by Kevin Rose of Phillip Rosedale, of Second Life. And they had an amazing discussion about how to find, hire and identify good programmer's, and how hard it is to find good ones. Which has lead me to really think about the way we programmer's learn, are taught. For a majority of us, myself included, we are self-taught. Which is great about being a programmer, anyone can learn and develop skills. But this also means, that there is no real standards of what a good programmer is/are, and what kind of environment's encourage the growth of programming skills. This isn't so much a question, but just a desire in me, to see how we can change the culture of programming, and the manager's of programming, so that education and self-improvement is encouraged. There are a lot of avenue's for continued education, youtube videos, books, conferences, but because of the experiental nature of what we do, it isn't always clear what's important to learn and to master. Let's look at the The Joel 12 Steps. The Joel Test Do you use source control? Can you make a build in one step? Do you make daily builds? Do you have a bug database? Do you fix bugs before writing new code? Do you have an up-to-date schedule? Do you have a spec? Do programmers have quiet working conditions? Do you use the best tools money can buy? Do you have testers? Do new candidates write code during their interview? Do you do hallway usability testing? I think all of these have important value, but because of something I call the Experiential Gap, if a programmer or manager has never experienced any of the negative consequences for not having done items on the list, they will never see the need to do any of them. The Experiental Gap, is my basic theory, that each of us has different jobs and different experiences. So for some of us, that have always worked with dozens of programmer's, source control is a must have. But for people who have always been the only programmer, they can not imagine the need for source control. And it's because of this major flaw in how we learn, that we evaluate people by what best practices they do or not do, and the reason for either can start a flame war. We always evaluate people in our field by what they do, and think "Oh if this guy/gal isn't doing xyz best practice, he/she can't be a good programmer, so let's not waste time or energy talking to them." This is exactly why we have so many programming flame wars, that it becomes, because of the Experiental Gap, we can't imagine people not having made the decisions that we have had to made. So this has lead me to think, that we totally need to rethink how we train, educate and manage programmer's. For example, what percentage of you have had encouragement by your manager's to go to conferences, and even have them pay for it? For me, and a lot of people, this is extremely rare, a lot of us would love to go to conferences, to learn more, but the money ain't there to do that. So the point of this question is really to spark a lot of how can we train, learn and manage better? How can we create a new culture of learning that doesn't insult people for not having the same job experiences. Yes we all have jobs and work to do, but our ability to do our jobs well, depends on our desire, interest and support in improving our mastery of our skills. Right now, I see our culture being rather disorganized, we support the elite, but those tons of us that want to get better, just don't have enough support to learn and improve ourselves. I mean, do we as an industry, want to be perceived as just replaceable cogs? Thank you...

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• ipv6 port 445 does not accept the request from a global type address

  - by blacktea

  I want to scan the port 445 in windows server 2003, but my scanner only have one type ipv6 address which is global not link-local. When I do this,I find that I can't find port 445 open. But I use the command "netstat -an" to assure the port 445 is listening. Finally I find this confusing phenomenon: 1.when I set a link-local ddress in my scanner, then it will work in scanning port 445. 2.when I only set a global address in my scanner, it doed not work. This means if a host with a link-local address use socket to send a syn packet to the port 445 in server 2003, it will receive a ack packet. But if with a global address it will receive a rst packet. Thus, I can't scan the port 445 in server 2003 with a global address. I need to know why? Can anybody help? And I use the netsh-firewall to check the exception and netsh-interface-ipv6 to turn off the firewall on the specific interface. Still can't establish the connection with port 445, do you have any ideal about this ?

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• Collision between sprites in game programming?

  - by Lyn Maxino

  I've since just started coding for an android game using eclipse. I've read Beginning Android Game Programming and various other e-books. Recently, I've encountered a problem with collision between sprites. I've used this code template for my program. package com.project.CAI_test; import java.util.Random; import android.graphics.Bitmap; import android.graphics.Canvas; import android.graphics.Rect; public class Sprite { // direction = 0 up, 1 left, 2 down, 3 right, // animation = 3 back, 1 left, 0 front, 2 right int[] DIRECTION_TO_ANIMATION_MAP = { 3, 1, 0, 2 }; private static final int BMP_ROWS = 4; private static final int BMP_COLUMNS = 3; private static final int MAX_SPEED = 5; private GameView gameView; private Bitmap bmp; private int x = 0; private int y = 0; private int xSpeed; private int ySpeed; private int currentFrame = 0; private int width; private int height; public Sprite(GameView gameView, Bitmap bmp) { this.width = bmp.getWidth() / BMP_COLUMNS; this.height = bmp.getHeight() / BMP_ROWS; this.gameView = gameView; this.bmp = bmp; Random rnd = new Random(); x = rnd.nextInt(gameView.getWidth() - width); y = rnd.nextInt(gameView.getHeight() - height); xSpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; ySpeed = rnd.nextInt(MAX_SPEED * 2) - MAX_SPEED; } private void update() { if (x >= gameView.getWidth() - width - xSpeed || x + xSpeed <= 0) { xSpeed = -xSpeed; } x = x + xSpeed; if (y >= gameView.getHeight() - height - ySpeed || y + ySpeed <= 0) { ySpeed = -ySpeed; } y = y + ySpeed; currentFrame = ++currentFrame % BMP_COLUMNS; } public void onDraw(Canvas canvas) { update(); int srcX = currentFrame * width; int srcY = getAnimationRow() * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bmp, src, dst, null); } private int getAnimationRow() { double dirDouble = (Math.atan2(xSpeed, ySpeed) / (Math.PI / 2) + 2); int direction = (int) Math.round(dirDouble) % BMP_ROWS; return DIRECTION_TO_ANIMATION_MAP[direction]; } public boolean isCollition(float x2, float y2) { return x2 > x && x2 < x + width && y2 > y && y2 < y + height; } } The above code only detects collision between the generated sprites and the surface border. What I want to achieve is a collision detection that is controlled by the update function without having to change much of the coding. Probably several lines placed in the update() function. Tnx for any comment/suggestion.

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• Reading graph inputs for a programming puzzle and then solving it

  - by Vrashabh

  I just took a programming competition question and I absolutely bombed it. I had trouble right at the beginning itself from reading the input set. The question was basically a variant of this puzzle http://codercharts.com/puzzle/evacuation-plan but also had an hour component in the first line(say 3 hours after start of evacuation). It reads like this This puzzle is a tribute to all the people who suffered from the earthquake in Japan. The goal of this puzzle is, given a network of road and locations, to determine the maximum number of people that can be evacuated. The people must be evacuated from evacuation points to rescue points. The list of road and the number of people they can carry per hour is provided. Input Specifications Your program must accept one and only one command line argument: the input file. The input file is formatted as follows: the first line contains 4 integers n r s t n is the number of locations (each location is given by a number from 0 to n-1) r is the number of roads s is the number of locations to be evacuated from (evacuation points) t is the number of locations where people must be evacuated to (rescue points) the second line contains s integers giving the locations of the evacuation points the third line contains t integers giving the locations of the rescue points the r following lines contain to the road definitions. Each road is defined by 3 integers l1 l2 width where l1 and l2 are the locations connected by the road (roads are one-way) and width is the number of people per hour that can fit on the road Now look at the sample input set 5 5 1 2 3 0 3 4 0 1 10 0 2 5 1 2 4 1 3 5 2 4 10 The 3 in the first line is the additional component and is defined as the number of hours since the resuce has started which is 3 in this case. Now my solution was to use Dijisktras algorithm to find the shortest path between each of the rescue and evac nodes. Now my problem started with how to read the input set. I read the first line in python and stored the values in variables. But then I did not know how to store the values of the distance between the nodes and what DS to use and how to input it to say a standard implementation of dijikstras algorithm. So my question is two fold 1.) How do I take the input of such problems? - I have faced this problem in quite a few competitions recently and I hope I can get a simple code snippet or an explanation in java or python to read the data input set in such a way that I can input it as a graph to graph algorithms like dijikstra and floyd/warshall. Also a solution to the above problem would also help. 2.) How to solve this puzzle? My algorithm was: Find shortest path between evac points (in the above example it is 14 from 0 to 3) Multiply it by number of hours to get maximal number of saves Also the answer given for the variant for the input set was 24 which I dont understand. Can someone explain that also. UPDATE: I get how the answer is 14 in the given problem link - it seems to be just the shortest path between node 0 and 3. But with the 3 hour component how is the answer 24 UPDATE I get how it is 24 - its a complete graph traversal at every hour and this is how I solve it Hour 1 Node 0 to Node 1 - 10 people Node 0 to Node 2- 5 people TotalRescueCount=0 Node 1=10 Node 2= 5 Hour 2 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5(Rescued) Node 0 to Node 1 = 10 Node 0 to Node 2 = 5 Node 1 to Node 2 = 4 TotalRescueCount = 10 Node 1 = 10 Node 2= 5+4 = 9 Hour 3 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5+4 = 9(Rescued) TotalRescueCount = 9+5+10 = 24 It hard enough for this case , for multiple evac and rescue points how in the world would I write a pgm for this ?

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• How to config socket connect timeout in C#

  - by ninikin

  (C# )When the Client tries to connect to a disconnected IP address, there is a long timeout over 15 seconds... How can we reduce this timeout? What is the method to config it? The code I'm using to set up a socket connection is as following: try { m_clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPAddress ip = IPAddress.Parse(serverIp); int iPortNo = System.Convert.ToInt16(serverPort); IPEndPoint ipEnd = new IPEndPoint(ip, iPortNo); m_clientSocket.Connect(ipEnd); if (m_clientSocket.Connected) { lb_connectStatus.Text = "Connection Established"; WaitForServerData(); } else { } } catch (SocketException se) { lb_connectStatus.Text = "Connection Failed"; MessageBox.Show(se.Message); }

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• Need help implementing simple socket server using GIOService (GLib, Glib-GIO)

  - by Mark Renouf

  I'm learning the basics of writing a simple, efficient socket server using GLib. I'm experimenting with GSocketService. So far I can only seem to accept connections but then they are immediately closed. From the docs I can't figure out what step I am missing. I'm hoping someone can shed some light on this for me. When running the following: # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. # telnet localhost 4000 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Connection closed by foreign host. Output from the server: # ./server New Connection from 127.0.0.1:36962 New Connection from 127.0.0.1:36963 New Connection from 127.0.0.1:36965 Current code: /* * server.c * * Created on: Mar 10, 2010 * Author: mark */ #include <glib.h> #include <gio/gio.h> gchar *buffer; gboolean network_read(GIOChannel *source, GIOCondition cond, gpointer data) { GString *s = g_string_new(NULL); GError *error; GIOStatus ret = g_io_channel_read_line_string(source, s, NULL, &error); if (ret == G_IO_STATUS_ERROR) g_error ("Error reading: %s\n", error->message); else g_print("Got: %s\n", s->str); } gboolean new_connection(GSocketService *service, GSocketConnection *connection, GObject *source_object, gpointer user_data) { GSocketAddress *sockaddr = g_socket_connection_get_remote_address(connection, NULL); GInetAddress *addr = g_inet_socket_address_get_address(G_INET_SOCKET_ADDRESS(sockaddr)); guint16 port = g_inet_socket_address_get_port(G_INET_SOCKET_ADDRESS(sockaddr)); g_print("New Connection from %s:%d\n", g_inet_address_to_string(addr), port); GSocket *socket = g_socket_connection_get_socket(connection); gint fd = g_socket_get_fd(socket); GIOChannel *channel = g_io_channel_unix_new(fd); g_io_add_watch(channel, G_IO_IN, (GIOFunc) network_read, NULL); return TRUE; } int main(int argc, char **argv) { g_type_init(); GSocketService *service = g_socket_service_new(); GInetAddress *address = g_inet_address_new_from_string("127.0.0.1"); GSocketAddress *socket_address = g_inet_socket_address_new(address, 4000); g_socket_listener_add_address(G_SOCKET_LISTENER(service), socket_address, G_SOCKET_TYPE_STREAM, G_SOCKET_PROTOCOL_TCP, NULL, NULL, NULL); g_object_unref(socket_address); g_object_unref(address); g_socket_service_start(service); g_signal_connect(service, "incoming", G_CALLBACK(new_connection), NULL); GMainLoop *loop = g_main_loop_new(NULL, FALSE); g_main_loop_run(loop); }

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• HTTP request, strange socket behavoir

  - by hoodoos

  I expirience strange behavior when doing HTTP requests through sockets, here the request: POST https://test.com:443/service/XMLSelect HTTP/1.1 Content-Length: 10926 Host: test.com User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 1.0.3705) Authorization: Basic XXX SOAPAction: http://test.com/SubmitXml Later on there goes body of my request with given content length. After that I recive something like: HTTP/1.1 200 OK Server: Apache-Coyote/1.1 Content-Type: text/xml;charset=utf-8 Transfer-Encoding: chunked Date: Tue, 30 Mar 2010 06:13:52 GMT So everything seem to be fine here. I read all contents from network stream and successfuly recieve response. But my socket which I'm doing polling on switches it's modes like that: write ( i write headers and request here ) read ( after headers sent i begin to recieve response ) write ( STRANGE BEHAVIOUR HERE. WHY? here i send nothing really ) read ( here it switches to read back again ) last two steps can repeat several times. So I want to ask what leads for socket's mode change? And in this case it's not a big problem, but when I use gzip compression in my request ( no idea how it's related ) and ask server to send gzipped response to me like this: POST https://test.com:443/service/XMLSelect HTTP/1.1 Content-Length: 1076 Accept-Encoding: gzip Content-Encoding: gzip Host: test.com User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 1.0.3705) Authorization: Basic XXX SOAPAction: http://test.com/SubmitXml I recieve response like that: HTTP/1.1 200 OK Server: Apache-Coyote/1.1 Content-Encoding: gzip Content-Type: text/xml;charset=utf-8 Transfer-Encoding: chunked Date: Tue, 30 Mar 2010 07:26:33 GMT 2000 ? I recieve a chunk size and GZIP header, it's all okay. And here's what is happening with my poor little socket meanwhile: write ( i write headers and request here ) read ( after headers sent i begin to recieve response ) write ( STRANGE BEHAVIOUR HERE. And it finally sits here forever waiting for me to send something! But if i refer to HTTP I don't have to send anything more! ) What can it be related to? What it wants me to send? Is it remote web server's problem or do I miss something? PS All actual service references and login/passwords replaced with fake ones :)

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• java.net.SocketException: Software caused connection abort: socket write error

  - by npinti

  Hi guys, I am trying to send an image from a Java desktop application to a J2ME application. The problem is that I am getting this exception: java.net.SocketException: Software caused connection abort: socket write error I have looked around on the net, and although this problem is not that rare, I was unable to find a concrete solution. I am transforming the image into a byte array before transferring it. These are the methods found on the desktop application and on the J2ME respectively public void send(String ID, byte[] serverMessage) throws Exception { //Get the IP and Port of the person to which the message is to be sent. String[] connectionDetails = this.userDetails.get(ID).split(","); Socket sock = new Socket(InetAddress.getByName(connectionDetails[0]), Integer.parseInt(connectionDetails[1])); OutputStream os = sock.getOutputStream(); for (int i = 0; i < serverMessage.length; i++) { os.write((int) serverMessage[i]); } os.flush(); os.close(); sock.close(); } private void read(final StreamConnection slaveSock) { Runnable runnable = new Runnable() { public void run() { try { DataInputStream dataInputStream = slaveSock.openDataInputStream(); int inputChar; StringBuffer results = new StringBuffer(); while ( (inputChar = dataInputStream.read()) != -1) { results.append((char) inputChar); } dataInputStream.close(); slaveSock.close(); parseMessage(results.toString()); results = null; } catch(Exception e) { e.printStackTrace(); Alert alertMsg = new Alert("Error", "An error has occured while reading a message from the server:\n" + e.getMessage(), null, AlertType.ERROR); alertMsg.setTimeout(Alert.FOREVER); myDisplay.setCurrent(alertMsg, resultScreen); } } }; new Thread(runnable).start(); } I am sending the message across a LAN, and I have no problems when I send short text messages instead of images. Also, I used wireshark and it seems that the desktop application is only sending part of the message. Any help would be highly appreciated. Also, everything works on the J2ME simulator. Thanks.

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• Decrypting data from a secure socket

  - by Ronald

  I'm working on a server application in Java. I've successfully got past the handshake portion of the communication process, but how do I go about decrypting my input stream? Here is how I set up my server: import java.io.IOException; import java.net.ServerSocket; import java.net.Socket; import java.util.ArrayList; import java.util.HashMap; import javax.net.ServerSocketFactory; import javax.net.ssl.SSLServerSocket; import javax.net.ssl.SSLServerSocketFactory; import org.json.me.JSONException; import dictionary.Dictionary; public class Server { private static int port = 1234; public static void main(String[] args) throws JSONException { System.setProperty("javax.net.ssl.keyStore", "src/my.keystore"); System.setProperty("javax.net.ssl.keyStorePassword", "test123"); System.out.println("Starting server on port: " + port); HashMap<String, Game> games = new HashMap<String, Game>(); final String[] enabledCipherSuites = { "SSL_RSA_WITH_RC4_128_SHA" }; try{ SSLServerSocketFactory socketFactory = (SSLServerSocketFactory) SSLServerSocketFactory.getDefault(); SSLServerSocket listener = (SSLServerSocket) socketFactory.createServerSocket(port); listener.setEnabledCipherSuites(enabledCipherSuites); Socket server; Dictionary dict = new Dictionary(); Game game = new Game(dict); //for testing, creates 1 global game. while(true){ server = listener.accept(); ClientConnection conn = new ClientConnection(server, game, "User"); Thread t = new Thread(conn); t.start(); } } catch(IOException e){ System.out.println("Failed setting up on port: " + port); e.printStackTrace(); } } } I used a BufferedReader to get the data send from the client: BufferedReader d = new BufferedReader(new InputStreamReader(socket.getInputStream())); After the handshake is complete it appears like I'm getting encrypted data. I did some research online and it seems like I might need to use a Cipher, but I'm not sure. Any ideas?

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• C# Socket Server

  - by Snoopy

  In .NET 3.5 a new socket classes was released: http://msdn.microsoft.com/en-us/library/bb968780.aspx i found a sample but some questions regarding best practicses are remaining: http://code.msdn.microsoft.com/nclsamples/Wiki/View.aspx?title=Socket%20Performance m_numConnections (the maximum number of connections the sample is designed to handle simultaneously) is probably equal to the amount of cpu cores i have. m_receiveBufferSize is the size for one packet? like 8kb? how should i handle a length byte? opsToPreAlloc i dont understand. is this if i code a transparent proxy? Regarding the multithreading, what should be used? The reactive extension seem to be a good choice. Has anyone tried this in a real world project? Are there better options? I had bad experiences with the .NET thread pool in the past.

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• How to rebind another UDP socket port properly?

  - by Jollian

  When my client application launchs, it binds the UDP port like this: this.BindPort(5001); The BindPort method implement blow: public void BindPort(int port) { m_listener = new Socket( AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp ); IPEndPoint Point = new IPEndPoint( IPAddress.Any, Port ); m_listener.Bind( port); m_listener.BeginReceive( buff, 0, buff.Length, SocketFlags.None, new AsyncCallback( DataReceived ), buff ); } And when my server application commands client to bind to another UDP port(e.g. 5005). I call the same BindPort method in client. Then a exception occurs at DataReceived method. I think there must be a problem that I don't close the UDP port properly. But how can i close the UDP socket properly and rebind to another one. Thanks.

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• Problem about socket communication

  - by Ahmet Altun

  I have two separate socket projects in VS.NET. One of them is sender, other one is receiver. After starting receiver, i send data from sender. Although send method returns 13 bytes as successfully transferred, the receiver receives 0 (zero). The receiver accepts sender socket and listens to it. But cannot receive data. Why? P.S. : If sender code is put in receiver project, receiver can get data, as well.

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• killing a separate thread having a socket

  - by user311906

  Hi All I have a separate thread ListenerThread having a socket listening to info broadcasted by some remote server. This is created at the constructor of one class I need to develop. Because of requirements, once the separate thread is started I need to avoid any blocking function on the main thread. Once it comes to the point of calling the destructor of my class I cannot perform a join on the listener thread so the only thing I can do is to KILL it. My questions are: what happens to the network resoruces allocated by the function passed to the thead? Is the socket closed properly or there might be something pending? ( most worried about this ) is this procedure fast enough i.e. is the thread killed so that interrupt immediately ? I am working with Linux ...what command or what can I check to ensure that there is no networking resource left pending or that something went wrong for the Operating system I thank you very much for your help Regards MNSTN NOTE: I am using boost::thread in C++

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• C# Socket ReceiveAll

  - by rielz

  Hey there! I am trying to capture ip packets in c#. Everything is working fine, except that i only get outgoing packets. My Code: using (Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP)) { sock.Bind(new IPEndPoint(LOCALHOST, 0)); sock.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.HeaderIncluded, true); sock.IOControl(IOControlCode.ReceiveAll, BitConverter.GetBytes(1), null); while (true) { byte[] buffer = new byte[sock.ReceiveBufferSize]; int count = sock.Receive(buffer); // ... } } Does anyone have an idea? :( Doesnt find any solutions at Google, ... Thank you in advance.

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• Socket ReceiveAll

  - by rielz

  I am trying to capture ip packets in c#. Everything is working fine, except that i only get outgoing packets. My Code: using (Socket sock = new Socket(AddressFamily.InterNetwork, SocketType.Raw, ProtocolType.IP)) { sock.Bind(new IPEndPoint(MYADDRESS, 0)); sock.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.HeaderIncluded, true); sock.IOControl(IOControlCode.ReceiveAll, BitConverter.GetBytes(1), null); while (true) { byte[] buffer = new byte[sock.ReceiveBufferSize]; int count = sock.Receive(buffer); // ... } } The problem is definitely my pc! But maybe there is a workaround ...

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• How did you get your first programming job?

  - by Gaz

  Hi All, I have some commercial programming experience although it was not my primary role (C# and Java), SCJP 6 cert, some SQL experience and have been doing a lot of Android programming (I have one app with 36,000 downloads). I have a degree in Chemistry and a Diploma in Programming (half a degree made up of 2nd/3rd year uni courses). I'm trying to get my first entry level programmer job but am finding it tough out there.......How did other people get there first jobs in programming?

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• Receiving broadcast packets using packet socket

  - by user314336

  Hello I try to send DHCP RENEW packets to the network and receive the responses. I broadcast the packet and I can see that it's successfully sent using Wireshark. But I have difficulties receiving the responses.I use packet sockets to catch the packets. I can see that there are responses to my RENEW packet using Wireshark, but my function 'packet_receive_renew' sometimes catch the packets but sometimes it can not catch the packets. I set the file descriptor using FDSET but the 'select' in my code can not realize that there are new packets for that file descriptor and timeout occurs. I couldn't make it clear that why it sometimes catches the packets and sometimes doesn't. Anybody have an idea? Thanks in advance. Here's the receive function. int packet_receive_renew(struct client_info* info) { int fd; struct sockaddr_ll sock, si_other; struct sockaddr_in si_me; fd_set rfds; struct timeval tv; time_t start, end; int bcast = 1; int ret = 0, try = 0; char buf[1500] = {'\0'}; uint8_t tmp[BUFLEN] = {'\0'}; struct dhcp_packet pkt; socklen_t slen = sizeof(si_other); struct dhcps* new_dhcps; memset((char *) &si_me, 0, sizeof(si_me)); memset((char *) &si_other, 0, sizeof(si_other)); memset(&pkt, 0, sizeof(struct dhcp_packet)); define SERVER_AND_CLIENT_PORTS ((67 << 16) + 68) static const struct sock_filter filter_instr[] = { /* check for udp */ BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 0, 4), /* L5, L1, is UDP? */ /* skip IP header */ BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0), /* L5: */ /* check udp source and destination ports */ BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0), BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */ /* returns */ BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ), /* L3: pass */ BPF_STMT(BPF_RET|BPF_K, 0), /* L4: reject */ }; static const struct sock_fprog filter_prog = { .len = sizeof(filter_instr) / sizeof(filter_instr[0]), /* casting const away: */ .filter = (struct sock_filter *) filter_instr, }; printf("opening raw socket on ifindex %d\n", info->interf.if_index); if (-1==(fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)))) { perror("packet_receive_renew::socket"); return -1; } printf("got raw socket fd %d\n", fd); /* Use only if standard ports are in use */ /* Ignoring error (kernel may lack support for this) */ if (-1==setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog, sizeof(filter_prog))) perror("packet_receive_renew::setsockopt"); sock.sll_family = AF_PACKET; sock.sll_protocol = htons(ETH_P_IP); //sock.sll_pkttype = PACKET_BROADCAST; sock.sll_ifindex = info->interf.if_index; if (-1 == bind(fd, (struct sockaddr *) &sock, sizeof(sock))) { perror("packet_receive_renew::bind"); close(fd); return -3; } if (-1 == setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &bcast, sizeof(bcast))) { perror("packet_receive_renew::setsockopt"); close(fd); return -1; } FD_ZERO(&rfds); FD_SET(fd, &rfds); tv.tv_sec = TIMEOUT; tv.tv_usec = 0; ret = time(&start); if (-1 == ret) { perror("packet_receive_renew::time"); close(fd); return -1; } while(1) { ret = select(fd + 1, &rfds, NULL, NULL, &tv); time(&end); if (TOTAL_PENDING <= (end - start)) { fprintf(stderr, "End receiving\n"); break; } if (-1 == ret) { perror("packet_receive_renew::select"); close(fd); return -4; } else if (ret) { new_dhcps = (struct dhcps*)calloc(1, sizeof(struct dhcps)); if (-1 == recvfrom(fd, buf, 1500, 0, (struct sockaddr*)&si_other, &slen)) { perror("packet_receive_renew::recvfrom"); close(fd); return -4; } deref_packet((unsigned char*)buf, &pkt, info); if (-1!=(ret=get_option_val(pkt.options, DHO_DHCP_SERVER_IDENTIFIER, tmp))) { sprintf((char*)tmp, "%d.%d.%d.%d", tmp[0],tmp[1],tmp[2],tmp[3]); fprintf(stderr, "Received renew from %s\n", tmp); } else { fprintf(stderr, "Couldnt get DHO_DHCP_SERVER_IDENTIFIER%s\n", tmp); close(fd); return -5; } new_dhcps->dhcps_addr = strdup((char*)tmp); //add to list if (info->dhcps_list) info->dhcps_list->next = new_dhcps; else info->dhcps_list = new_dhcps; new_dhcps->next = NULL; } else { try++; tv.tv_sec = TOTAL_PENDING - try * TIMEOUT; tv.tv_usec = 0; fprintf(stderr, "Timeout occured\n"); } } close(fd); printf("close fd:%d\n", fd); return 0; }

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• C socket programming: recv / select not seeing sent messages

  - by Fantastic Fourier

  Hey guys, I had some questions, about socket programming for client-server using TCP/IP. I am using select() to recv(), which works fine when client send() messages to server, but not the other way around. The send() returns positive (and reasonable) numbers of bytes sent by server but I know that the nubmer of bytes "sent" really means "sent out of the socket", not "sent and was received by the client." The select() function seems to work fine. So given that, my guess is that it's the send() function that is giving me the problem. Probably the address of client in send() is not correct. But when I compared address.sin_addr.s_addrmember (it's an unsigned long int) of struct sockaddr_in from recv() and send() of server, they are identical. So I am kind of lost as to what could be wrong?

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• Socket Programming for the Web

  - by Benny

  I have to interact with a legacy system that accepts socket communication and messages. My goal is to make the application cross-platform, but I need the ability to push messages to the client (i.e. - .NET's WCF, Java's Comet) and detect when the user closes out of their browser to destroy the socket. I have built a prototype of .NET wrapper + WCF + Silverlight but it is so disconnected it is difficult to manage the state of the user and seems to be a nightmare to support. All of that considered, what would be my best option?

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• Waiting for ServerSocket accept() to put socket into "listen" mode

  - by inazaruk

  I need a simple client-server communication in order to implement unit-test. My steps: Create server thread Wait for server thread to put server socket into listen mode ( serverSocket.accept() ) Create client Make some request, verify responses Basically, I have a problem with step #2. I can't find a way to signal me when server socket is put to "listen" state. An asynchronous call to "accept" will do in this case, but java doesn't support this (it seems to support only asynchronous channels and those are incompatible with "accept()" method according to documentation). Of cause I can put a simple "sleep", but that is not really a solution for production code. So, to summarize, I need to detect when ServerSocket has been put into listen mode without using sleeps and/or polling.

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