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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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  • 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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  • 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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  • [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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  • 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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  • Linking ?++ - BDB - LNK2001

    - by MInner
    BDB is compiled on the same PC, under same VS. #include <db_cxx.h> int main(){ Db b(NULL, 0); return 0; } 1main.obj : error LNK2001: unresolved external symbol ""public: virtual __thiscall Db::~Db(void)" (??1Db@@UAE@XZ)" 1main.obj : error LNK2001: unresolved external symbol ""public: __thiscall Db::Db(class DbEnv *,unsigned int)" (??0Db@@QAE@PAVDbEnv@@I@Z)" what could be wrong?

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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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  • .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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  • Udp server sending only 0 bytes of data

    - by mawia
    Hi all, This is a simple Udp server.I am trying to transmit data to some clients,but unfortunetly it is unable to transmit data.Though send is running quite successfully but it is returning with a return value meaning it has send nothing.On the client they are receiving but again obviously,zero bytes. void* UdpServerStreamToClients(void *fileToServe) { int sockfd,n=0,k; struct sockaddr_in servaddr,cliaddr; socklen_t len; char dataToSend[1000]; sockfd=socket(AF_INET,SOCK_DGRAM,0); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr=htonl(INADDR_ANY); servaddr.sin_port=htons(32000); bind(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr)); FILE *fp; if((fp=fopen((char*)fileToServe,"r"))==NULL) { printf("can not open file "); perror("fopen"); exit(1); } int dataRead=1; while(dataRead) { len = sizeof(cliaddr); if((dataRead=fread(dataToSend,1,500,fp))<0) { perror("fread"); exit(1); } //sleep(2); for(list<clientInfo>::iterator it=clients.begin();it!=clients.end();it++) { cliaddr.sin_family = AF_INET; inet_aton(inet_ntoa(it->addr.sin_addr),&cliaddr.sin_addr); cliaddr.sin_port = htons(it->udp_port); n=sendto(sockfd,dataToSend,sizeof(dataToSend),0,(struct sockaddr *)&cliaddr,len); cout<<"number of bytes send by udp: "<< n << endl; printf("SEND this message %d : %s to %s :%d \n",n,dataToSend,inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port)); } } } I am checking the value of sizeof(dataTosend) and it is pretty much as expected ie thousand ie the size of buffer. Are you people seeing some possible flaw in it. All of the help in this regard will be appreciated. Thanks!

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  • Socket receive buffer size

    - by Kanishka
    Is there a way to determine the receive buffer size of a TCPIP socket in c#. I am sending a message to a server and expecting a response where I am not sure of the receive buffer size. IPEndPoint ipep = new IPEndPoint(IPAddress.Parse("192.125.125.226"),20060); Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); server.Connect(ipep); String OutStr= "49|50|48|48|224|48|129|1|0|0|128|0|0|0|0|0|4|0|0|32|49|50"; byte[] temp = OutStr.Split('|').Select(s => byte.Parse(s)).ToArray(); int byteCount = server.Send(temp); byte[] bytes = new byte[255]; int res=0; res = server.Receive(bytes); return Encoding.UTF8.GetString(bytes);

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  • udp server unable to transmit data

    - by mawia
    Hi! all, I have written a simple udp server which has to transmit certain data to few of it's clients. but though server is successfully executing send,but unable to transmit even a single byte.The return value of send is 0 although I have enough data to be transmitted.you can see the code for the said server here: http://pastebin.com/zeMcwd6X Can you people help in finding the possible culprit for the same.Any reply in this regard will be appreciated. Lot of Thanks in advance! Mawia

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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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  • EOF error using recv in python

    - by tipu
    I am doing this in my code, HOST = '192.168.1.3' PORT = 50007 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((HOST, PORT)) query_details = {"page" : page, "query" : query, "type" : type} s.send(str(query_details)) #data = eval(pickle.loads(s.recv(4096))) data = s.recv(16384) But I am continually getting EOF at the last line. The code I am sending with, self.request.send(pickle.dumps(results))

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  • python send/receive hex data via TCP socket

    - by Mike
    I have a ethenet access control device that is said to be able to communicate via TCP. How can i send a pachet by entering the HEX data, since this is what i have from their manual (a standard format for the communication packets sent and received after each command)

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  • Interview Questions that can be asked on TCP/IP, UDP, Socket Programming ?

    - by Shantanu Gupta
    I am going for an interview day after tomorrow where i will be asked vaious questions related to TCP/IP and UDP. As of now i have prepared theoritical knowledge about it. But now I am looking up for gaining some practicle knowledge related to how it works in a network. What all is going in vaious .NET classes. I want to create a very small application like a chat or something that can make me all these concepts very much clear. Could you please suggest some questions related to TCP/IP that you generally ask or that you might have faced. How communication is going from server to client. Right now I am studying TcpClient, TcpListener and UdpClient Class but I want to implement all of them so as to get aware about its working. Is Chat application a Tcp/IP application ? I would appreciate your help.

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  • Functioning Socket read no longer works when called in AsyncTask

    - by bibismcbryde
    I'm making an app that sends a string to a server over a socket and then reads the output after the server has processed that data. It worked perfectly when it was my foreground task, but I have since used AsyncTask to show a process dialog while the socket communication runs in the background, and things start breaking after I read the output from the server and then try to close the socket. private class Progressor extends AsyncTask<String, Void, Void> { ProgressDialog dialog; protected void onPreExecute() { dialog = ProgressDialog.show(ClearTalkInputActivity.this, "Loading..", "Analyzing Text", true, false); } protected Void doInBackground(String... strings) { String language = strings[0].toLowerCase(); String the_text = strings[1]; Socket socket = null; DataOutputStream dos = null; DataInputStream dis = null; try { socket = new Socket(my_ip, port); dos = new DataOutputStream(socket.getOutputStream()); dis = new DataInputStream(socket.getInputStream()); dos.writeUTF(language+"****"+the_text); String in = ""; while (in.indexOf("</content>") < 0) { in += dis.readUTF(); } socket.close(); save_str(OUTPUT_KEY, in); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { if (socket != null) { try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } if (dos != null) { try { dos.close(); } catch (IOException e) { e.printStackTrace(); } } if (dis != null) { try { dis.close(); } catch (IOException e) { e.printStackTrace(); } } return null; } protected void onPostExecute() { if (dialog.isShowing()) dialog.dismiss(); startActivity(new Intent (output_intent)); } }

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  • Why does my Perl TCP server script hang with many TCP connections?

    - by viraptor
    I've got a strange issue with a server accepting TCP connections. Even though there are normally some processes waiting, at some volume of connections it hangs. Long version: The server is written in Perl and binds a $srv socket with the reuse flag and listen == 5. Afterwards, it forks into 10 processes with a loop of $clt=$srv->accept(); do_processing($clt); $clt->shutdown(2); The client written in C is also very simple - it sends some lines, then receives all lines available and does a shutdown(sockfd, 2); There's nothing async going on and at the end both send and receive queues are empty (as reported by netstat). Connections last only ~20ms. All clients behave the same way, are the same implementation, etc. Now let's say I'm accepting X connections from client 1 and another X from client 2. Processes still report that they're idle all the time. If I add another X connections from client 3, suddenly the server processes start hanging just after accepting. The first blocking thing they do after accept(); is while (<$clt>) ... - but they don't get any data (on the first try already). Suddenly all 10 processes are in this state and do not stop waiting. On strace, the server processes seem to hang on read(), which makes sense. There are loads of connections in TIME_WAIT state belonging to that server (~100 when the problem starts to manifest), but this might be a red herring. What could be happening here?

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  • How can I obtain the IPv4 address of the client?

    - by Dr Dork
    Hello! I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code setup to listen for incoming TCP connection requests from clients after the parent socket has been created and is set to listen... int sockfd, newfd; unsigned int len; socklen_t sin_size; char msg[]="Test message sent"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char ip[INET6_ADDRSTRLEN]; . . //parent socket creation and listen code omitted for simplicity . //wait for connection requests from clients while(1) { //Returns the socketID and address of client connecting to socket if( ( newfd = accept(sockfd, (struct sockaddr *)&client, &len) ) == -1 ){ perror("Accept"); exit(-1); } if( (rv = recv(newfd, buf, MAXLEN-1, 0 )) == -1) { perror("Recv"); exit(-1); } struct sockaddr_in *clientAddr = ( struct sockaddr_in *) get_in_addr((struct sockaddr *)&client); inet_ntop(client.ss_family, clientAddr, ip, sizeof ip); printf("Receive from %s: query type is %s\n", ip, buf); if( ( st = send(newfd, msg, strlen(msg), 0)) == -1 ) { perror("Send"); exit(-1); } //ntohs is used to avoid big-endian and little endian compatibility issues printf("Send %d byte to port %d\n", ntohs(clientAddr->sin_port) ); close(newfd); } } I found the get_in_addr function online and placed it at the top of my code and use it to obtain the IP address of the client connecting... // 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); } but the function always returns the IPv6 IP address since thats what the sa_family property is set as. My question is, is the IPv4 IP address stored anywhere in the data I'm using and, if so, how can I access it? Thanks so much in advance for all your help!

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  • How Proxy server works with tcp/http connections?

    - by Vivek
    Since I am a beginner in the world of internet/networking, I always mess up with these kinds of doubts in my head while programming ;) .. My doubts are, While working behind a proxy, how my requests and responses work? Means my request headers and data will first reach to Proxy server- then proxy server sends it(same headers and data) to corresponding server. And server responses to it with a response header and body to the proxy server-then proxy server sends it to my computer. Wright? While using websockets we are upgrading our http connection to tcp. At this time what is happening @ Proxy server? Does the proxyserver also upgrades its connection to plain TCP? After opening such TCP connections, does the proxy server able to track/log those socket messsages? And most importantly, Is the proxy server transparent or acting like an original server infront of a client? Thanks for any answers or helpful links in advance.

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  • C++ Boost ASIO: how to read/write with a timeout?

    - by Stéphane
    From reading other Stackoverflow entries and the boost::asio documentation, I've confirmed that there is no synchronous asio read/write calls that also provide an easy-to-use timeout as a parameter to the call. I'm in the middle of converting an old-school linux socket app with select(2) calls that employs timeouts, and I need to do more-or-less the same. So what is the best way to do this in boost::asio? Looking at the asio documentation, there are many confusing examples of various things to do with timers, but I'm quite confused. I'd love to see a simple-to-read example of this: Read from a socket, but wait for a maximum of X seconds after which the function either returns with nothing, or returns with whatever it was able to read from the socket before the timeout expired.

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  • How to determine IP used by client connecting to INADDR_ANY listener socket in C

    - by codebox_rob
    I have a network server application written in C, the listener is bound using INADDR_ANY so it can accept connections via any of the IP addresses of the host on which it is installed. I need to determine which of the server's IP addresses the client used when establishing its connection - actually I just need to know whether they connected via the loopback address 127.0.0.1 or not. Partial code sample as follows (I can post the whole thing if it helps): static struct sockaddr_in serverAddress; serverAddress.sin_family = AF_INET; serverAddress.sin_addr.s_addr = INADDR_ANY; serverAddress.sin_port = htons(port); bind(listener, (struct sockaddr *) &serverAddress, sizeof(serverAddress)); listen(listener, CONNECTION_BACKLOG); SOCKET socketfd; static struct sockaddr_in clientAddress; ... socketfd = accept(listener, (struct sockaddr *) &clientAddress, &length);

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  • scoket connection issue+php

    - by Abhimanyu
    Hi, I am using PHP socket programming and able to write data to open socket but i have to wait for a long time(or stuck it)for the response or some time getting error like "Maximum execution time of 30 seconds exceeded line number where this code is placed fgets($fp, 128), i have check the server it seems it has sent the response as expected but i am not getting why i m unable to get response.following the code using for socket connection and reading data. functon scoket_connection() { $fp = fsockopen(CLIENT_HOST,CLIENT_PORT, $errno, $errstr); fwrite($fp,$packet); $msg = fgets($fp, 128); fclose($fp) return $msg; } any idea???

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