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  • Programming error in Java Socket

    - by Akhil K Nambiar
    Can you tell me what is the error in this code? Socket socket = new Socket(hostname, port); PrintWriter out = new PrintWriter(socket.getOutputStream(), true); //DataInputStream is = new DataInputStream(socket.getInputStream()); out.println("hi"); System.out.print(in.readLine()); The Server Socket program is written in .Net and it echoes back the data. The data is sent successfully but could not be retrieved properly. I tried the same by using the linux command nc 192.168.1.6 8425 (enter) Hi (Sent data) Hi (recieved data) When I checked the code the data is found to have sent as byteStream in .Net. Is that a problem. In that case what modification should I make.

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  • [Errno 10061] No connection could be made because the target machine actively refused it

    - by user551717
    I've tried to connect to my local machine every time I try and run my program. I am a nub, so it's probably a simple mistake somewhere. def connect(self): self.conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM) self.conn.connect((self.host,self.port)) That is the code causing the error. The host and port are defined. Why is it giving me this error report? [Errno 10061] No connection could be made because the target machine actively refused it

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  • how to print a char from struct

    - by make
    Hi Could someone please tell us to print a char when receiving data as a struct? Here is an example: ... struct rcv{ int x1; float x2; char *x3; }; rcv data_rcv; ... if (recv(socket, &data_rcv, sizeof(data_rcv), 0) < 0) printf("recv() failed"); ... printf("x1 = %d\n", data_rcv.x1); printf("x2 = %f\n", data_rcv.x2); printf("x3 = %s\n", data_rcv.x3); // it doesn't print anything, why? ... Thanks for your replies-

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  • Is there a way to get the uid of the other end of a unix socket connection

    - by yuyichao
    Is there a way for a unix socket listener to only accept connection from certain user (chmod/chown does not work for abstract socket afaik), or in another word, get the uid of the incoming connection (on Linux)? Dbus, which uses abstract unix socket on Linux, has a function GetConnectionUnixUser which is used by polkit to determine the caller. So I suppose the dbus-daemon must have a way to do that. Does anyone know how that works? THX

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  • How to write an Android SocketServer to listen on wifi

    - by xioxox
    I've written a thread using java.net.SocketServer to listen on a particular port. It works fine in the android simulator (using port forwarding). I'm planning to connect over wifi to this port when the app is being used. However, the SocketServer documentation says that if you don't supply an InetAddress, the server listens on localhost. Am I correct that if I do not supply the address, I will not be able to get a connection over wifi? How can I get the InetAddress of the wifi connection to pass to the SocketServer?

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  • Android , Read in binary data and write it to file

    - by Shpongle
    Hi all , Im trying to read in image file from a server , with the code below . It keeps going into the exception. I know the correct number of bytes are being sent as I print them out when received. Im sending the image file from python like so #open the image file and read it into an object imgfile = open (marked_image, 'rb') obj = imgfile.read() #get the no of bytes in the image and convert it to a string bytes = str(len(obj)) #send the number of bytes self.conn.send( bytes + '\n') if self.conn.sendall(obj) == None: imgfile.flush() imgfile.close() print 'Image Sent' else: print 'Error' Here is the android part , this is where I'm having the problem. Any suggestions on the best way to go about receiving the image and writing it to a file ? //read the number of bytes in the image String noOfBytes = in.readLine(); Toast.makeText(this, noOfBytes, 5).show(); byte bytes [] = new byte [Integer.parseInt(noOfBytes)]; //create a file to store the retrieved image File photo = new File(Environment.getExternalStorageDirectory(), "PostKey.jpg"); DataInputStream dis = new DataInputStream(link.getInputStream()); try{ os =new FileOutputStream(photo); byte buf[]=new byte[1024]; int len; while((len=dis.read(buf))>0) os.write(buf,0,len); Toast.makeText(this, "File recieved", 5).show(); os.close(); dis.close(); }catch(IOException e){ Toast.makeText(this, "An IO Error Occured", 5).show(); } EDIT: I still cant seem to get it working. I have been at it since and the result of all my efforts have either resulted in a file that is not the full size or else the app crashing. I know the file is not corrupt before sending server side. As far as I can tell its definitely sending too as the send all method in python sends all or throws an exception in the event of an error and so far it has never thrown an exception. So the client side is messed up . I have to send the file from the server so I cant use the suggestion suggested by Brian .

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  • PHP socket UDP communication

    - by Ghedeon
    Server works fine, but the problem is the client doesn't receive anything. server.php <?php $buf_size = 1024; $socket = stream_socket_server("udp://127.0.0.1:3127", $errno, $errstr, STREAM_SERVER_BIND); do { $str = stream_socket_recvfrom($socket, $buf_size, 0, $peer); $str = "abc"; stream_socket_sendto($socket, $str, strlen($str), 0, $peer); } while (true); ?> client.php <?php $fp = stream_socket_client("udp://127.0.0.1:3127", $errno, $errstr); if (!$fp) { echo "$errno - $errstr<br />\n"; } else { fwrite($fp, "1 2 3"); echo fread($fp, 15); fclose($fp); } ?>

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  • Reason for socket.error

    - by August Flanagan
    Hi, I am a complete newbie when it comes to python, and programming in general. I've been working on a little webapp for the past few weeks trying to improve my coding chops. A few days ago my laptop was stolen so I went out and got a new MacBook Pro. Thank God I had everything under subversion control. The problem is now that I am on my new machine a script that I was running has stopped working and I have no idea why. This is really the only part of what I have been writing that I borrowed heavily for existing scripts. It is from the widely available whois.py script and I have only slightly modified it as follows (see below). It was running fine on my old system (running ubuntu), but now the socket.error is being raised. I'm completely lost on this, and would really appreciate any help. Thanks! def is_available(domainname, whoisserver="whois.verisign-grs.com", cache=0): if whoisserver is None: whoisserver = "whois.networksolutions.com" s = None while s == None: try: s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setblocking(0) try: s.connect((whoisserver, 43)) except socket.error, (ecode, reason): if ecode in (115, 150): pass else: raise socket.error, (ecode, reason) ret = select.select([s], [s], [], 30) if len(ret[1])== 0 and len(ret[0]) == 0: s.close() raise TimedOut, "on connect " s.setblocking(1) except socket.error, (ecode, reason): print ecode, reason time.sleep(1) s = None s.send("%s \n\n" % domainname) page = "" while 1: data = s.recv(8196) if not data: break page = page + data s.close()

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  • [java] Threading socket handler for two sided communication in tcp port

    - by raven
    I want to make a chat which will be programed in java. one computer will host the server and the other one will initiate the socket [tcp port]. now from what I read there should be a loop that will constantly read the socket which means it will make the code stuck. I have a button that is 'actionperformed' on mouse release, I want to know if it will work along with the loops that constantly reads the socket so that it will also send the infromation I wrote. If I must thread it, I want to know if the run() method must be void because if I thread it it will mean creating a new class, and the whole GUI is one big class which includes a text area, and it's private. also how can I extract the information from the socket directly to the text area? lets say the textarea variable is called "chatOutput". thx :)

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  • What happens to an instance of ServerSocket blocked inside accept(), when I drop all references to i

    - by Hanno Fietz
    In a multithreaded Java application, I just tracked down a strange-looking bug, realizing that what seemed to be happening was this: one of my objects was storing a reference to an instance of ServerSocket on startup, one thread would, in its main loop in run(), call accept() on the socket while the socket was still waiting for a connection, another thread would try to restart the component under some conditions, the restart process missed the cleanup sequence before it reached the initialization sequence as a result, the reference to the socket was overwritten with a new instance, which then wasn't able to bind() anymore the socket which was blocking inside the accept() wasn't accessible anymore, leaving a complete shutdown and restart of the application as the only way to get rid of it. Which leaves me wondering: with no references left to the ServerSocket instance, what would free the socket for a new connection? At what point would the ServerSocket become garbage collected? In general, what are good practices I can follow to avoid this type of bug?

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  • How can I forcibly close a TcpListener

    - by Nissim
    I have a service which communicates through tcpListener. Problem is when the user restarts the service - an "Address already in use" exception is thrown, and the service cannot be started for a couple of minutes or so. Is there's any way of telling the system to terminate the old connection so I can open a new one? (I can't just use random ports because there is no way for the service to notify the clients what is the port, so we must depend on a predefined port)

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  • non blocking TCP-acceptor not reading from socket

    - by Abruzzo Forte e Gentile
    I have the code below implementing a NON-Blocking TCP acceptor. Clients are able to connect without any problem and the writing seems occurring as well, but the acceptor doesn't read anything from the socket and the call to read() blocks indefinitely. Am I using some wrong setting for the acceptor? Kind Regards AFG int main(){ create_programming_socket(); poll_programming_connect(); while(1){ poll_programming_read(); } } int create_programming_socket(){ int cnt = 0; p_listen_socket = socket( AF_INET, SOCK_STREAM, 0 ); if( p_listen_socket < 0 ){ return 1; } int flags = fcntl( p_listen_socket, F_GETFL, 0 ); if( fcntl( p_listen_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ return 1; } bzero( (char*)&p_serv_addr, sizeof(p_serv_addr) ); p_serv_addr.sin_family = AF_INET; p_serv_addr.sin_addr.s_addr = INADDR_ANY; p_serv_addr.sin_port = htons( p_port ); if( bind( p_listen_socket, (struct sockaddr*)&p_serv_addr , sizeof(p_serv_addr) ) < 0 ) { return 1; } listen( p_listen_socket, 5 ); return 0; } int poll_programming_connect(){ int retval = 0; static socklen_t p_clilen = sizeof(p_cli_addr); int res = accept( p_listen_socket, (struct sockaddr*)&p_cli_addr, &p_clilen ); if( res > 0 ){ p_conn_socket = res; int flags = fcntl( p_conn_socket, F_GETFL, 0 ); if( fcntl( p_conn_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){ retval = 1; }else{ p_connected = true; } }else if( res == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): accept(c_listen_socket) would block\n"); }else{ retval = 1; } return retval; } int poll_programming_read(){ int retval = 0; bzero( p_buffer, 256 ); int numbytes = read( p_conn_socket, p_buffer, 255 ); if( numbytes > 0 ) { fprintf( stderr, "poll_sock(): read() read %d bytes\n", numbytes ); pkt_struct2_t tx_buf; int fred; int i; } else if( numbytes == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) { //printf( "poll_sock(): read() would block\n"); } else { close( p_conn_socket ); p_connected = false; retval = 1; } return retval; }

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  • How do you make sure your pakcet is delivered to right client using public ip address

    - by TemporaryNickName
    So private IP addresses are 192.168.00 ~ 192.168.255.255 or 10.0.0.0 or 172.16.0.0 ~ 172.31.255.255 If I accepted a client to my serversocket, I can get the client's remoteIp address by using socket.getremotesocketaddress(); But I suspect the IP address that I'm getting from this method is only the public IP address and it must have more than one client using same public IP as this one (one like you see when you go on to the website www.whatismyip.com). So if I want to make sure that my packet is delivered to the right person using some IP address or otherthing that uniquely identifies a person, what should I have to do?

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  • Strange numbers in java socket output

    - by user293163
    I have small test app: Socket socket = new Socket("jeck.ru", 80); PrintWriter pw = new PrintWriter(socket.getOutputStream(), false); pw.println("GET /ip/ HTTP/1.1"); pw.println("Host: jeck.ru"); pw.println(); pw.flush(); BufferedReader rd = new BufferedReader(new InputStreamReader(socket.getInputStream())); String str; while ((str = rd.readLine()) != null) { System.out.println(str); } It`s output: HTTP/1.1 200 OK Date: Sat, 13 Mar 2010 22:06:51 GMT Content-Type: text/html;charset=utf-8 Transfer-Encoding: chunked Connection: keep-alive Keep-Alive: timeout=5 Server HTTP/1.1 200 OK Date: Sat, 13 Mar 2010 22:06:51 GMT Content-Type: text/html;charset=utf-8 Transfer-Encoding: chunked Connection: keep-alive Keep-Alive: timeout=5 Server: Apache Cache-Control: max-age=0 Expires: Sat, 13 Mar 2010 22:06:51 GMT 123 <!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>??? IP</title> </head> <body> <div style='text-align: center; font: 32pt Verdana;margin-top: 300px'> ??? IP &#151; 94.103.87.153 </div> </body> </html> 0 Whence these numbers (123 an 0) takes?

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  • Does Socket open another thread? Does it return something?

    - by Roman
    In the client application I call new Socket(serverIP,serverPort). As a result the client application sends a request to the server application to open a socket. Does it start a new thread? I mean which of the following is true? Client application sends a request and immediately starts to execute following commands (not weighting for the answer). Client sends the request and weights for the answer. As soon as the answer is obtained, the client application continues to execute following commands. The second case seems to be more realistic and logical for me. However, I do not understand what happens if the server does not open a socket and it does not say that it does not "want" to open the second (it can happen if the server does not exist or network is broken). What will happen in this case? Will server weight forever? In general it would be nice for the client to know what is the result of its request for the socket. For example I can imagine the following situations: The socket is opened by the server. The server refuses to open a socket. So, server exists, it got the request from the client but it says "no". There is no response from the server. I know that new Socket(serverIP,serverPort) does not "return" this kind of information. But it throws exceptions. One of them is "UnkownHostException". When it is thrown? When the server is not responding for a while (for how long)? ADDED: I just found out that UnknownHostException is thrown to indicate that the IP address of a host could not be determined. So, it is unrelated with the above described situations (server is not responding, server refuses to open a socket).

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  • Socket php server not showing messages sent from android client

    - by Mj1992
    Hi I am a newbie in these kind of stuff but here's what i want to do. I am trying to implement a chat application in which users will send their queries from the website and as soon as the messages are sent by the website users.It will appear in the android mobile application of the site owner who will answer their queries .In short I wanna implement a live chat. Now right now I am just simply trying to send messages from android app to php server. But when I run my php script from dreamweaver in chrome the browser keeps on loading and doesn't shows any output when I send message from the client. Sometimes it happened that the php script showed some outputs which I have sent from the android(client).But i don't know when it works and when it does not. So I want to show those messages in the php script as soon as I send those messages from client and vice versa(did not implemented the vice versa for client but help will be appreciated). Here's what I've done till now. php script: <?php set_time_limit (0); $address = '127.0.0.1'; $port = 1234; $sock = socket_create(AF_INET, SOCK_STREAM, 0); socket_bind($sock, $address, $port) or die('Could not bind to address'); socket_listen($sock); $client = socket_accept($sock); $welcome = "Roll up, roll up, to the greatest show on earth!\n? "; socket_write($client, $welcome,strlen($welcome)) or die("Could not send connect string\n"); do{ $input=socket_read($client,1024,1) or die("Could not read input\n"); echo "User Says: \n\t\t\t".$input; if (trim($input) != "") { echo "Received input: $input\n"; if(trim($input)=="END") { socket_close($spawn); break; } } else{ $output = strrev($input) . "\n"; socket_write($spawn, $output . "? ", strlen (($output)+2)) or die("Could not write output\n"); echo "Sent output: " . trim($output) . "\n"; } } while(true); socket_close($sock); echo "Socket Terminated"; ?> Android Code: public class ServerClientActivity extends Activity { private Button bt; private TextView tv; private Socket socket; private String serverIpAddress = "127.0.0.1"; private static final int REDIRECTED_SERVERPORT = 1234; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); bt = (Button) findViewById(R.id.myButton); tv = (TextView) findViewById(R.id.myTextView); try { InetAddress serverAddr = InetAddress.getByName(serverIpAddress); socket = new Socket(serverAddr, REDIRECTED_SERVERPORT); } catch (UnknownHostException e1) { e1.printStackTrace(); } catch (IOException e1) { e1.printStackTrace(); } bt.setOnClickListener(new OnClickListener() { public void onClick(View v) { try { EditText et = (EditText) findViewById(R.id.EditText01); String str = et.getText().toString(); PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true); out.println(str); Log.d("Client", "Client sent message"); } catch (UnknownHostException e) { tv.setText(e.getMessage()); e.printStackTrace(); } catch (IOException e) { tv.setText(e.getMessage()); e.printStackTrace(); } catch (Exception e) { tv.setText(e.getMessage()); e.printStackTrace(); } } }); } } I've just pasted the onclick button event code for Android.Edit text is the textbox where I am going to enter my text. The ip address and port are same as in php script.

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  • Java blocking socket returning incomplete ByteBuffer

    - by evandro-carrenho
    I have a socketChannel configured as blocking, but when reading byte buffers of 5K from this socket, I get an incomplete buffer sometimes. ByteBuffer messageBody = ByteBuffer.allocate(5*1024); messageBody.mark(); messageBody.order(ByteOrder.BIG_ENDIAN); int msgByteCount = channel.read(messageBody); Ocasionally, messageBody is not completely filled and channel.read() does not return -1 or an exception, but the actual number of bytes read (which is less than 5k). Has anyone experienced a similar problem?

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  • Waiting for data via select not working

    - by BSchlinker
    I'm currently working on a project which involves multiple clients connected to a server and waiting for data. I'm using select and monitoring the connection for incoming data. However, the client just continues to print nothing, acting as if select has discovered incoming data. Perhaps I'm attacking this wrong? For the first piece of data the server does send, it is displayed correctly. However, the server then disconnects and the client continues to spew blank lines. FD_ZERO(&readnet); FD_SET(sockfd, &readnet); while(1){ rv = select(socketdescrip, &readnet, NULL, NULL, &timeout); if (rv == -1) { perror("select"); // error occurred in select() } else if (rv == 0) { printf("Connection timeout! No data after 10 seconds.\n"); } else { // one or both of the descriptors have data if (FD_ISSET(sockfd, &readnet)) { numbytes = recv(sockfd, buf, sizeof buf, 0); printf("Data Received\n"); buf[numbytes] = '\0'; printf("client: received '%s'\n",buf); sleep(10); } } }

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  • Raw socket implementation in windows?

    - by krishnakumar
    I need to create TCP/IP headers manually for my application. For that i used Raw socket. My system os is win xp (SP3). My code compiles fine :) but it throws a run time error: Initialising Winsock...Initialised successfully. Creating Raw TCP Socket...Raw TCP Socket Created successfully. Setting the socket in RAW mode...Successful. Enter hostname : 192.168.1.152 Resolving Hostname...Resolved. Enter Source IP : 192.168.1.151 Sending packet... Error sending Packet : 10022 I have set IP_HDRINCL to 1. What am i doing wrong? I switched off the firewall too but still get the same result.

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  • How can I force the server socket to re-accept a request from a client?

    - by Roman
    For those who does not want to read a long question here is a short version: A server has an opened socket for a client. The server gets a request to open a socket from the same client-IP and client-port. I want to fore the server not to refuse such a request but to close the old socket and open a new one. How can I do ti? And here is a long (original) question: I have the following situation. There is an established connection between a server and client. Then an external software (Bonjour) says to my client the it does not see the server in the local network. Well, client does nothing about that because of the following reasons: If Bonjour does not see the server it does not necessarily means that client cannot see the server. Even if the client trusts the Bonjour and close the socket it does not improve the situation ("to have no open socket" is worser that "to have a potentially bad socket"). So, client do nothing if server becomes invisible to Bonjour. But than the server re-appears in the Bonjour and Bonjour notify the client about that. In this situation the following situations are possible: The server reappears on a new IP address. So, the client needs to open a new socket to be able to communicate with the server. The server reappears on the old IP address. In this case we have two subcases: 2.1. The server was restarted (switched off and then switched on). So, it does not remember the old socket (which is still used by the client). So, client needs to close the old socket and open a new one (on the same server-IP address and the same server-port). 2.2. We had a temporal network problem and the server was running the whole time. So, the old socket is still available for the use. In this case the client does not really need to close the old socket and reopen a new one. But to simplify my life I decide to close and reopen the socket on the client side in any case (in spite on the fact that it is not really needed in the last described situation). But I can have problems with that solution. If I close the socket on the client side and than try to reopen a socket from the same client-IP and client-port, server will not accept the call for a new socket. The server will think that such a socket already exists. Can I write the server in such a way, that it does not refuse such calls. For example, if it (the server) sees that a client send a request for a socket from the same client-IP and client-port, it (server) close the available socket, associated with this client-IP and client-port and than it reopens a new socket.

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  • [C++] Adding a string or char array to a byte vector

    - by xeross
    I'm currently working on a class to create and read out packets send through the network, so far I have it working with 16bit and 8bit integers (Well unsigned but still). Now the problem is I've tried numerous ways of copying it over but somehow the _buffer got mangled, it segfaulted, or the result was wrong. I'd appreciate if someone could show me a working example. My current code can be seen below. Thanks, Xeross Main #include <iostream> #include <stdio.h> #include "Packet.h" using namespace std; int main(int argc, char** argv) { cout << "#################################" << endl; cout << "# Internal Use Only #" << endl; cout << "# Codename PACKETSTORM #" << endl; cout << "#################################" << endl; cout << endl; Packet packet = Packet(); packet.SetOpcode(0x1f4d); cout << "Current opcode is: " << packet.GetOpcode() << endl << endl; packet.add(uint8_t(5)) .add(uint16_t(4000)) .add(uint8_t(5)); for(uint8_t i=0; i<10;i++) printf("Byte %u = %x\n", i, packet._buffer[i]); printf("\nReading them out: \n1 = %u\n2 = %u\n3 = %u\n4 = %s", packet.readUint8(), packet.readUint16(), packet.readUint8()); return 0; } Packet.h #ifndef _PACKET_H_ #define _PACKET_H_ #include <iostream> #include <vector> #include <stdio.h> #include <stdint.h> #include <string.h> using namespace std; class Packet { public: Packet() : m_opcode(0), _buffer(0), _wpos(0), _rpos(0) {} Packet(uint16_t opcode) : m_opcode(opcode), _buffer(0), _wpos(0), _rpos(0) {} uint16_t GetOpcode() { return m_opcode; } void SetOpcode(uint16_t opcode) { m_opcode = opcode; } Packet& add(uint8_t value) { if(_buffer.size() < _wpos + 1) _buffer.resize(_wpos + 1); memcpy(&_buffer[_wpos], &value, 1); _wpos += 1; return *this; } Packet& add(uint16_t value) { if(_buffer.size() < _wpos + 2) _buffer.resize(_wpos + 2); memcpy(&_buffer[_wpos], &value, 2); _wpos += 2; return *this; } uint8_t readUint8() { uint8_t result = _buffer[_rpos]; _rpos += sizeof(uint8_t); return result; } uint16_t readUint16() { uint16_t result; memcpy(&result, &_buffer[_rpos], sizeof(uint16_t)); _rpos += sizeof(uint16_t); return result; } uint16_t m_opcode; std::vector<uint8_t> _buffer; protected: size_t _wpos; // Write position size_t _rpos; // Read position }; #endif // _PACKET_H_

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  • .net 3.5 message framing

    - by Rob
    We have message framing working by using a lengh prefix but using .NET 2.0 beginSend/BeginReceive. Is message framing any different in 3.5, if so how should we implement it using the new framework? Are there any useable examples out there which focus purely on message framing using 3.5? Many thanks

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