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  • can't connect Java client to C server.

    - by nexes
    I have a very simple server written in C and an equally simple client written in Java. When I run them both on the same computer everything works, but when I try to run the server on computer A and the client on computer B, I get the error IOException connection refused from the java client. I can't seem to find out whats happening, any thoughts? I've even turned off the firewalls but the problem still persists. server. #include <stdio.h> #include <unistd.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #define PORT 3557 #define BUF 256 int main(int argc, char *argv[]) { struct sockaddr_in host, remote; int host_fd, remote_fd; int size = sizeof(struct sockaddr);; char data[BUF]; host.sin_family = AF_INET; host.sin_addr.s_addr = htonl(INADDR_ANY); host.sin_port = htons(PORT); memset(&host.sin_zero, 0, sizeof(host.sin_zero)); host_fd = socket(AF_INET, SOCK_STREAM, 0); if(host_fd == -1) { printf("socket error %d\n", host_fd); return 1; } if(bind(host_fd, (struct sockaddr *)&host, size)) { printf("bind error\n"); return 1; } if(listen(host_fd, 5)) { printf("listen error"); return 1; } printf("Server setup, waiting for connection...\n"); remote_fd = accept(host_fd, (struct sockaddr *)&remote, &size); printf("connection made\n"); int read = recv(remote_fd, data, BUF, 0); data[read] = '\0'; printf("read = %d, data = %s\n", read, data); shutdown(remote_fd, SHUT_RDWR); close(remote_fd); return 0; } client. import java.net.*; import java.io.*; public class socket { public static void main(String[] argv) { DataOutputStream os = null; try { Socket socket = new Socket("192.168.1.103", 3557); os = new DataOutputStream(socket.getOutputStream()); os.writeBytes("phone 12"); os.close(); socket.close(); } catch (UnknownHostException e) { System.out.println("Unkonw exception " + e.getMessage()); } catch (IOException e) { System.out.println("IOException caught " + e.getMessage()); } } }

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  • TCP/IP Implementation General Questions

    - by user2971023
    I've implemented the concepts shown here; http://wiki.unity3d.com/index.php/Simple_TCP/IP_Client_-_Server outside of unity and it works. (though i had to create the TCPIPServerApp from scratch as i could not find the base project anywhere). I have some general questions on how to use tcp/ip properly however. I've done some research on tcp/ip itself but I'm still a little confused. It seems like using the method above doesn't guarantee that I'll see the message (res). It just checks on every update to see if there is a different message in res. What if multiple messages are sent and the program lags or something, will i miss the earlier packet(s)? Should i instead do an array so it stores the last X messages? How do i know the data was received? Do I need to add a message id and build in my own ack into the data? Should i check to see if the port is in use before setting up a connection? Sorry for all the questions. This is all new to me but I enjoy this very much! ... Below already answered By Anton, Thanks It sounds like tcp uses its own packet numbering to ensure the packets end up in the right order on the other side. What if a packet is missed, are the subsequent packets thrown away? Or is this numbering and packet ordering, only for handling data that is broken out into multiple packets? TCP will automatically break the data into multiple packets if necessary right?

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  • How to manually close connection in BaseHTTPServer?

    - by user1657188
    I have a script that sends a request to an HTTP server. HTTP server script (snippet): ... class MyHandler(BaseHTTPServer.BaseHTTPRequestHandler): def do_GET(sa): pdict = cgi.parse_header(sa.headers.getheader('referer')) q = pdict[0] q = urllib.unquote(q) if q == "enternetixplorer" # basically just ignore this, doesn't have to do with the question sa.wfile.write("blah blah blah") # now restart server httpd.server_close() python = sys.executable os.execl(python, python, * sys.argv) ... The "blah blah blah" is sent back, but the connection does not seem to close, and my script is waiting forever until I abort the server. (My thought is BaseHTTPServer automatically closes connection when the last part in "do_GET()" is computed, but I prevent this by restarting the script.) If I'm right, how do I close the connection? If not, what else might be the problem? Edit: The server script HAS to restart the entire program.

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  • sockaddr_in causing segfault?

    - by Curlystraw
    Working on creating a server/client system in C right now, and I'm having a little trouble with the client part. From what I've seen, I need to use sockaddr_in so I can connect to the server. However, I've been getting a segfault every time. I believe that sockaddr_in has something to do with it, as comment it and it's references later in the program fixes the segfault. code: #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <unistd.h> #include <netinet/in.h> int main(int argc, char** argv) { int Csock; int con; char *data = 0; char buf[101] = ""; struct sockaddr_in addr; Csock = socket(AF_INET, SOCK_STREAM, 0); addr.sin_family = AF_INET; addr.sin_port = htons(3435); con = connect(Csock, (struct sockaddr*) &addr, sizeof(&addr)); write(con, "Text", sizeof("Text")); *data = read(con, buf, 100); puts(data); return 0; } sadly, I am rather new to C, so that's as much as I can figure... can anyone tell me a way to go about eliminating the segfault? Thanks!

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  • Weird send() problem (with Wireshark log)

    - by Meta
    I had another question about this issue, but I didn't ask properly, so here I go again! I'm sending a file by sending it in chunks. Right now, I'm playing around with different numbers for the size of that chunk, to see what size is the most efficient. When testing on the localhost, any chunk size seems to work fine. But when I tested it over the network, it seems like the maximum chunk size is 8191 bytes. If I try anything higher, the transfer becomes extremely, painfully, slow. To show what happens, here are the first 100 lines of Wireshark logs when I use a chunk size of 8191 bytes, and when I use a chunk size of 8192 bytes: (the sender is 192.168.0.102, and the receiver is 192.168.0.100) 8191: http://pastebin.com/E7jFFY4p 8192: http://pastebin.com/9P2rYa1p Notice how in the 8192 log, on line 33, the receiver takes a long time to ACK the data. This happens again on line 103 and line 132. I believe this delay is the root of the problem. Note that I have not modified the SO_SNDBUF option nor the TCP_NODELAY option. So my question is, why am I getting delayed ACKs when sending files in chunks of 8192 bytes, when everything works fine when using chunks of 8191 bytes? Edit: As an experiment, I tried to do the file transfer in the other direction (from 192.168.0.100 to 192.168.0.102), and surprisingly, any number worked! (Although numbers around 8000 seemed to perform the smoothest). So then the problem is with my computer! But I'm really not sure what to check for. Edit 2: Here is the pseudocode I use to send and receive data.

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  • Send files between python and C#

    - by SuitUp
    Hi, i would like to know, what is the best way to send files between python and C# and vice versa. I have my own protocol which work on socket level, and i can send string and numbers in both ways. Loops works too. With this i can send pretty much anything, like package of users id, if it is simple data. But soon i will start sending whole files, maybe xml or executables. Simple server with files is no an option because i want sending files from client too. I was thinking about serialization but i don't know it is the best solution, but if it is i will love some tips from stackoverflow community.

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  • Socket stops communicating

    - by user1392992
    I'm running python 2.7 code on a Raspberry Pi that receives serial data from an Arduino, processes it, and sends it to a Windows box over a wifi link. The Pi is wired to a Linksys router running in client bridge mode and that router connects over wifi to another Linksys router to which the Windows box is wired. The code in the Pi runs fine for some (apparently) random interval, and then the Pi becomes unreachable from the Windows box. I'm running PUTTY on the the Windows machine to connect to the Pi and when the fail occurs I get a message saying there's been a network error and the Pi is not reachable. Pinging the Pi from the Windows machine works fine until the error, at which time it produces "Reply from 192.168.0.129: Destination host unreachable." The client bridge router to which the Pi is connected remains reachable. I've got the networking code on the Pi wrapped in an exception handler, and when it fails it shows the following: Ethernet problem: Traceback (most recent call last): File "garage.py", line 108, in module s.connect((host, port)) File "/usr/lib/python2.7/socket.py", line 224, in meth return getattr(self._sock,name)(*args) error: [Errno 113] No route to host None The relevant python code looks like: import socket import traceback host = '192.168.0.129' port = 31415 in the setup, and after serial data has been processed: try: bline = strline.encode('utf-8') s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect((host, port)) s.send(bline) s.close() except: print "Ethernet problem: " print traceback.print_exc() Where strline contains the processed data. As I said, this runs fine for a few hours more or less before failing. Any ideas? EDIT: When PUTTY fails its error message is :Network Error: Software caused connection abort."

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  • Interrupt a thread in DatagramSocket.receive

    - by SEK
    I'm building an application that listens on both TCP and UDP, and I've run into some trouble with my shutdown mechanism. When I call Thread.interrupt() on each of the listening threads, the TCP thread is interrupted from listening, whereas the UDP listener isn't. To be specific, the TCP thread uses Socket.accept(), which simply returns (without actually connecting). Whereas the UDP thread uses DatagramSocket.receive, and doesn't exit that method. Is this an issue in my JRE, my OS, or should I just switch to (Datagram)Socket.close()?

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  • Socket send recv functions

    - by viswanathan
    I have created a socket using the following lines of code. Now i change the value of the socket i get like this m_Socket++; Even now the send recv socket functions succeeds without throwing SOCKET_ERROR. I expect that it must throw error. Am i doing something wrong. struct sockaddr_in ServerSock; // Socket address structure to bind the Port Number to listen to char *localIP ; SOCKET SocServer; //To Set up the sockaddr structure ServerSock.sin_family = AF_INET; ServerSock.sin_addr.s_addr = INADDR_ANY; ServerSock.sin_port = htons(pLantronics->m_wRIPortNo); // To Create a socket for listening on wPortNumber if(( SocServer = socket( AF_INET, SOCK_STREAM, 0 )) == INVALID_SOCKET ) { return FALSE; } //To bind the socket with wPortNumber if(bind(SocServer,(sockaddr*)&ServerSock,sizeof(ServerSock))!=0) { return FALSE; } // To Listen for the connection on wPortNumber if(listen(SocServer,SOMAXCONN)!=0) { return FALSE; } // Structure to get the IP Address of the connecting Entity sockaddr_in insock; int insocklen=sizeof(insock); //To accept the Incoming connection on the wPortNumber pLantronics->m_Socket=accept(SocServer,(struct sockaddr*)&insock,&insocklen); if(pLantronics->m_Socket == INVALID_SOCKET) { shutdown(SocServer, 2 ); closesocket(SocServer ); return FALSE; } // To make socket non-blocking DWORD dwNonBlocking = 1; if(ioctlsocket( pLantronics->m_Socket, FIONBIO, &dwNonBlocking )) { shutdown(pLantronics->m_Socket, 2); closesocket(pLantronics->m_Socket); return FALSE; } pLantronics->m_sModemName = inet_ntoa(insock.sin_addr); Now i do m_Socket++;//change to some other number ideally expecting send recv to fail. Even now the send recv socket functions succeeds without throwing SOCKET_ERROR. I expect that it must throw error. Am i doing something wrong.

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  • Is select function internaly call tcp connect ?

    - by Syedsma
    Code Sinnpet: int CreateaTCPSocket() { int iSockID = ACE_OS::socket(......); ACE_OS::set_flags(iSockID,O_NONBLOCK); ACE_OS::bind(); if (ACE_OS::connect(iSockID ,....) < 0) { if (ACE_OS::select(.....,timeout) <= 0) { return INVALID_HANDLE; } } return iSockID; } My question is when connect is failed for non-block error and select is called and say select return success then again we need to call connect or select function internal do connect?

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  • Increase a recive buffer in UDP socket

    - by unresolved_external
    I'wm writing an app, which transmits video and obviously uses UDP protocol fot this purpose. So I am wondering how can I increase a size of send/recieve buffer, cause currently the maximal size of data, which I can send is 65000 bytes. I already tried to do it in following way: int option = 262144; if(setsockopt(m_SocketHandle,SOL_SOCKET,SO_RCVBUF ,(char*)&option,sizeof(option)) < 0) { printf("setsockopt failed\n"); } But it did not work. So how can I do it?

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  • MySQL, PHP, and Apache errors while connecting to DB

    - by cypherdelton
    I'm having two errors when I test the "mysql_connect()" function in php. I just installed PHP and MySQL from scratch. These errors may be related, so I will post them both here: Warning: mysql_connect() [function.mysql-connect]: Headers and client library minor version mismatch. Headers:50158 Library:50518 in /usr/local/apache2/htdocs/index.php on line 6 Warning: mysql_connect() [function.mysql-connect]: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) in /usr/local/apache2/htdocs/index.php on line 6 Many websites say to start the mysql server if you are getting error #2. Whenever I execute the command mysqld start --user=mysql I get the error "mysqld: Too many arguments (first extra is 'start'); Adding the "&" to the end of the command makes no difference (I don't know if it is supposed to). Thanks, Cypher Delton

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  • C# equivalent of recv?

    - by mlh
    Hello, I have a portion of C code that I am trying to port over to C#. In my C code, I create a socket and then issue a receive command. The receive command is void receive(mysocket, char * command_buffer) { recv(mysocket, command_buffer, COMMAND_BUFFER_SIZE, 0); } now, the command buffer is returned with new values including command_buffer[8] being a pointer to a string. I'm really confused as to how to do this in C# because C# Read() command specifically takes in bytes and not char. The important part is that I get the pointer to the string. Any ideas?

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  • Maintaining many socket connections with a single thread

    - by John
    Many tutorials on socket communication I see seem to use 1 thread per socket. But on a server used for online gaming, you might have 10k concurrent users - 10k threads isn't probably a wonderful idea. I came across a tool (SmartFox) which claims to use a single thread for monitoring all socket connections, potentially thousands of them. This app happens to be in Java, but I figure C++ or C# could do the same... how would you achieve this?

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  • Send files between python+django and C#

    - by SuitUp
    Hi, i would like to know, what is the best way to send files between python and C# and vice versa. I have my own protocol which work on socket level, and i can send string and numbers in both ways. Loops works too. With this i can send pretty much anything, like package of users id, if it is simple data. But soon i will start sending whole files, maybe xml or executables. Simple server with files is no an option because i want sending files from client too. I was thinking about serialization but i don't know it is the best solution, but if it is i will love some tips from stackoverflow community. EDIT: I added django to question and chose using http.

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  • Why my java app for android not connect to server?

    - by FredVaz
    Why my java app for android not connect to server ? I run the aplication in android emulator, and the server wich port 9999 and host 127.0.0.1 in my pc, but just not connect and i think this method isn't good for android app. It is my source code: import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; //Java imports //import android.util.Log; import java.io.*; import java.net.*; import java.util.*; import java.util.logging.Level; import java.util.logging.Logger; public class MainActivity extends Activity { //Variaveis Interface private Button ligar; private Button enviar; private EditText text1; private TextView text2; //Variaveis static Socket cSocket; static PrintWriter out; static BufferedReader in; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //Declaração butões ligar = (Button) findViewById(R.id.ligar); enviar = (Button) findViewById(R.id.enviar); text1 = (EditText) findViewById(R.id.text1); text2 = (TextView) findViewById(R.id.text2); //Interacao ligar.setOnClickListener(new OnClickListener(){ public void onClick(View arg0){ connect(); } }); enviar.setOnClickListener(new OnClickListener(){ public void onClick(View arg0){ out.println("Hello"); text2.setText(""); } }); } //Outras Funcoes public void connect(){ //Funcao ligar cSocket = null; out = null; in = null; try { cSocket = new Socket("127.0.0.1",9999); out = new PrintWriter(cSocket.getOutputStream(), true); in = new BufferedReader(new InputStreamReader(cSocket.getInputStream())); text2.setText("Estas conectado com sucesso."); } catch (IOException ex) { //Logger.getLogger(client.class.getName()).log(Level.SEVERE, null, ex); text2.setText("Erro! Na conexão"); } } // }

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  • C# Client-Server implementation error on client's socket

    - by Ksice
    I'm trying to launch my client. Server already runned on the same computer. So I'm using "localhost" with GetHostEntry: IPHostEntry ipHostInfo = System.Net.Dns.GetHostEntry("localhost"); IPAddress ipAddress = ipHostInfo.AddressList[0]; IPEndPoint remoteEP = new IPEndPoint(ipAddress, Port); But I have this "no connection could be made because the target machine actively refused it" error. What is the reason? Could it be because ipHostInfo.AddressList[0] is an IPv6? How then I can accept Ipv4 address?

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  • [Java] Listening for TCP and UDP requests on the same port

    - by user339328
    I am writing a Client/Server set of programs Depending on the operation requested by the client, I use make TCP or UDP request. Implementing the client side is straight-forward, since I can easily open connection with any protocol and send the request to the server-side. On the servers-side, on the other hand, I would like to listen both for UDP and TCP connections on the same port. Moreover, I like the the server to open new thread for each connection request. I have adopted the approach explained in: link text I have extended this code sample by creating new threads for each TCP/UDP request. This works correctly if I use TCP only, but it fails when I attempt to make UDP bindings. Please give me any suggestion how can I correct this. tnx

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  • Poblem with "CFDataRef".

    - by zp26
    Hello I have a problem with "CFDataRef. I get the "data" field from a "kCFSocketDataCallBack. "data" should correspond to a string received on the socket. How do I convert, for example, in a NSString so I can put my text in a textbox?? Thank you very much static void AcceptDataCallback(CFSocketRef s, CFSocketCallBackType type, CFDataRef address, const void *data, void *info) { //my code for the textBox }

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  • Send a String[] ArrayList over Socket connection

    - by Duncan Palmer
    So i'm trying to send a String[] Array/List over an open socket connection. I currently have this code: Sending: public void sendData() { try { OutputStream socketStream = socket.getOutputStream(); ObjectOutputStream objectOutput = new ObjectOutputStream(socketStream); objectOutput.writeObject(new String[] {"Test", "Test2", "Test3"}); objectOutput.close(); socketStream.close(); } catch (Exception e) { System.out.println(e.toString()); } } Recieving: public Object readData() { try { InputStream socketStream = socket.getInputStream(); ObjectInputStream objectInput = new ObjectInputStream(new GZIPInputStream(socketStream)); Object a = objectInput.readObject(); return a; } catch(Exception e) { return null; } } After I have recieved the String array/list on the other end I want to be able to iterate through it like I would do normally so I can get the values. My current code doesn't seem to works as it returns null as the value. is this possible?

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  • Running Java Server Application 24/7 (NOT on local machine) ...?

    - by Steven
    I am currently experimenting with Java Socket Programming and succeeded in creating a simple application that allows me to send data back and forth between a client and a server. I don't want to power my laptop (on which the server application runs) 24/7. Therefore, of course, no computer (that runs my client application) will be able to communicate with my selfmade server application as long as my laptop is turned off. Now I'd like to know: (1) Is it possible to run the server application on a remote (physical) server, so that I don't need my laptop for that purpose? (2) If yes, do you have any suggestions where I could rent such a remote server? As I said, I'm just curious about how all that stuff works. I don't really something expensive.

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  • Python server open all ports

    - by user1670178
    I am trying to open all ports using this code, why can I not create a loop to perform this function? http://www.kellbot.com/2010/02/tutorial-writing-a-tcp-server-in-python/ #!/usr/bin/python # This is server.py file ##server.py from socket import * #import the socket library n=1025 while n<1050: ##let's set up some constants HOST = '' #we are the host PORT = n #arbitrary port not currently in use ADDR = (HOST,PORT) #we need a tuple for the address BUFSIZE = 4096 #reasonably sized buffer for data ## now we create a new socket object (serv) ## see the python docs for more information on the socket types/flags serv = socket( AF_INET,SOCK_STREAM) ##bind our socket to the address serv.bind((ADDR)) #the double parens are to create a tuple with one element serv.listen(5) #5 is the maximum number of queued connections we'll allow serv = socket( AF_INET,SOCK_STREAM) ##bind our socket to the address serv.bind((ADDR)) #the double parens are to create a tuple with one element serv.listen(5) #5 is the maximum number of queued connections we'll allow print 'listening...' n=n+1 conn,addr = serv.accept() #accept the connection print '...connected!' conn.send('TEST') conn.close() How do I make this work so that I can specify input range and have the server open all ports up to 65535? #!/usr/bin/python # This is server.py file from socket import * #import the socket library startingPort=input("\nPlease enter starting port: ") startingPort=int(startingPort) #print startingPort def connection(): ## let's set up some constants HOST = '' #we are the host PORT = startingPort #arbitrary port not currently in use ADDR = (HOST,PORT) #we need a tuple for the address BUFSIZE = 4096 #reasonably sized buffer for data def socketObject(): ## now we create a new socket object (serv) serv = socket( AF_INET,SOCK_STREAM) def bind(): ## bind our socket to the address serv = socket( AF_INET,SOCK_STREAM) serv.bind((ADDR)) #the double parens are to create a tuple with one element serv.listen(5) #5 is the maximum number of queued connections we'll allow serv = socket( AF_INET,SOCK_STREAM) print 'listening...' def accept(): conn,addr = serv.accept() #accept the connection print '...connected!' conn.send('TEST') def close(): conn.close() ## Main while startingPort<65535: connection() socketObject() bind() accept() startingPort=startingPort+1

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  • Can two different UDP socket in a system bind same port?

    - by swift
    I have an application which uses UDP connection, now when i try to run the app more than once its throwing me an exception java.net.BindException: Address already in use: Cannot bind but in my another app, which uses tcp connection, i can open two instance of the same app and its working fine. why this error only with UDP connection?

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  • Interrupt mechanism in C,C++

    - by mawia
    Hey I was writing a udp client server in which a client waits for packets from server.But I want to limit this wait for certain time.After client don't get response for a certain moment in raise an alarm,basically it comes out and start taking remedy steps.So what are the possible solution for it.I think writing a wrapper around recv will work but how exactly this has to be done,I mean how will make recv raise alarm for you after that time limit. Any Help in this regard will be appreciated. Thanks!

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