Programming :: Poll() System Call Not Returning When The Socket Is Closed Locally?
Sep 29, 2010
we have a multi threaded program on Linux where one thread is waiting on poll() system call with event set to POLLIN, & another thread has closed the same socket fd (which is passed to poll) , but the poll() did not return, is this the expected behavior? From man page of poll we found that the poll should return POLLNVAL if the socket fd is closed, is my understanding correct or is there any bug in the poll()?In Solaris we observed that the poll system call is returning with POLLNVAL if the socket is closed.
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Mar 8, 2011
iam just trying to connect to server which accepts one client and server will read(blocking operation) infinitely, but After closing the client socket the server "read operation" is returning zero and "errno variable(in errno.h)" value is also zero. how can i detect whether a client socket is closed/active..?
client.c
Serv_Addr.sin_family = AF_INET;
Serv_Addr.sin_addr.s_addr = inet_addr("127.0.0.1");
Serv_Addr.sin_port = htons(26553);
if( 0 > connect (Serv_Fds,&Serv_Addr,sizeof(Serv_Addr)) )
{
perror("connect");
return 0;
[Code]....
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Aug 6, 2010
Reading some examples on net and copying some codes I was able to build a (frankstein) server that accept connection from one client and receive and send messages to it. The big problem that shows up is that I don't know when client disconnects from my server.
I've been looking for a solution, but no success. I'd read about SO_KEEPALIVE option (which could solve my problem), but I don't know how to use it (how to check the value of it).
I can't use ping because the server (machine) could be running, but not the client (software).
Anyone knows a good tutorial or how to (for beginners like me xD) of TcpIp sockets using c/c++ and how to detect when a client disconnect?
I don't know sockets very well.
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Jul 14, 2009
How to use execv from kernel space to call a user space program writtenfor socket prog.
I tried to write code for socket in kernel but its not working.
Socket code in kernel is also needed.
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Nov 6, 2010
I have been assigned to implement a system call that report the system statistics over all memory which are
Total Pages in Active LRU list
Total Pages in Inactive LRU List
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May 27, 2010
How do I poll for a page on a server using PHP?
If a user wanted a page that does not yet exist - but is being made at request - I'd like the script to "poke" the server to see if the page is ready to be displayed. If so, it would then transfer to that newly made page.
I read about "http_get", but do not seem to get it to work
Quote:
Ok, there might be a simple way out, but I don't see it.
My info came from [url]
More specific:
Quote:
Returns the HTTP response(s) as string on success, or FALSE on failure.
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Apr 3, 2011
in below program why was new_args[0], rather than the reference the_cmd, passed to the execvp system call?
Code:
/*
A _very_ limited shell program
[code]....
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Feb 26, 2010
I have a java application that I wrote recently. It runs off port 9955. The application runs great on my mac server. When I installed it on my linux box i cant get to it from outside the box. A port scan shows the port as closed. I flushed my iptables, did not help. I can telnet into the app locally, from the server and it works great. I cannot telnet from outside the server. I have a reference to the application in /etc/services as a tcp port (which it is).
netstat shows it as listening
netstat --listen
tcp6 0 0 [::]: SimpleSocketTest [::]:* LISTEN
netstat -anp | grep 9955
tcp6 0 0 ::: 9955 :::* LISTEN 1484/java
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Dec 8, 2010
I have a process that forks, where the childs puts some data of random size and exits while the parent should get the data and does some manipulation.. here I have used a pipe for child to write the data and parent to read the data.. Child simply dumps the data, and the data is of any size even child and parent doesnt know.
I have used select in the parent to see whether there is any data coming on the reading end of the pipe.. if there is a data.. I copy into a buffer.. Im reading the data continusly when the child exits after closing the writing end of pipe. Parent gets blocked on the read part But my question is how parent know the other of pipe is closed when using the select call. In otherwords.. while using select in readfds, how would i know the other end has closed the pipe..
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Sep 18, 2010
I am trying to figure out how i would go about finding out where system call is made and error checking is not done. I have code below, if somebody can point me in the right direction where system call is made but error checking is not done.Quote:
#include "shell.h"
#include <stdio.h>
#include <string.h>
[code]....
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Aug 30, 2010
I successfully added a new system call in CentOS Kernel but I don't know where to view it! My kernel version is -2.6.32.5
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Mar 24, 2011
how to create a new system call Linux? what is the process of creating ?my project is to create a system call for displaying owner of a file..where exactly we have to write the system call code? and where are the places need to change ?
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Dec 9, 2009
While creating a new VM for Win2K, I guet the following error when I try to "Finish":
Code:
Unable to complete install '<class 'libvirt.libvirtError'> socket closed unexpectedly
Traceback (most recent call last):
File "/usr/share/virt-manager/virtManager/create.py", line 717, in do_install
dom = guest.start_install(False, meter = meter)
[code]....
This looks like a SELinux issue, since I do get a warning: SELinux is preventing qemu (qemu_t) "search" to / (fusefs_t). I'm attaching the complete SELinux Alert.
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Apr 2, 2009
I want to test my system call that be goint to add to kernel, But when i finish compiling kernel, i found my system call code not work. the code i want to return the system time "struct timespec":
/*----------Start of mycall.c----------*/
#include <linux/linkage.h>
#include <linux/time.h>
#include <linux/kernel.h>
[code]....
so i want a method to test the new system call before compiling kernel.
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May 6, 2011
Anyone know the reason why a sleep( ) on a Redhat Linux OS would cause the system to indefinitely hang? It's doing this every 10 or so calls in my program and I have to press the reboot button on my computer. My program is reading from a UDP port that has messages sent to it 20 times per second. When I sleep I assume the internal UDP buffer is getting more and more filled.
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Dec 7, 2010
Anyone knows the difference between a socket and TCP connection for connecting to an external system?
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Apr 2, 2011
i've written small tool in C which makes measurements on my router (OpenWrt White Russian).
It is working as a deamon. If the tool is started manually, everything works fine. If it is started per script on startup, the following system call doesn't work :
Code: sprintf(command,"/bin/cat /root/%s%s | /usr/bin/ssh -p2222 user(at)host -i /root/.ssh/id_rsa "/bin/cat >> result/%s%s"", apmac, source, apmac, dest);
rc = system (command); the returned rc in this case is 256.
first i thought it is a problems with the user rights for the tool, so i have added +s to it. but that didn't help. as i said, when the daemon is started by hand, the system call works fine.
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Jul 30, 2011
I am making a library, but I am facing a strange problem while sending data over network using ethernet.
I am sending 39 bytes of the data from one server to slave application but some time slave receives 39 bytes and some time it receives 29 bytes. And when ever slave receives 29 bytes all the memories to which my pointers are pointing get changed. This problem is only when I am sending data from the server to slave, while sending data from slave to server I am facing no such issue.
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Sep 8, 2010
I have a script for dd command and i am using it in an application using system() call. Now i want to have the output of the script file (i.e output of dd command) in the application file itself.
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Nov 29, 2010
In practice I have a script that call a java program that call a linux system command. The script if I run it, from a shell functions well,so it is not a java problem. The problem come out when i put this script in a crontab schedulation. The result in this case is that java do not execute the system command. I think it depends on crontab
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Nov 20, 2010
Does anyone have straightforward simple example document for adding a system call on fedora 14 kernel?
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Dec 10, 2010
I have the following code:
Code:
#include <stdio.h>
#include <stdlib.h>
int main() {
system("ps -ef | grep myprocessname");
return 0; }
When I run this program it outputs the following list of running processes:
Code:
root 10279 10275 0 13:02 ? 00:00:00 myprocessname myvar1=value1 myvar2=value2
root 10341 10337 1 13:02 ? 00:00:00 myprocessname myvar1=value1 myvar2=value2
What I want to really do is instead of writing the output to screen I want to read the output and parse the various values value1, value2 etc. What is the best way to do this?
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Jul 6, 2010
i'm writing a simple program of client socket program. Here below is the code sample which i'm writing...
Code:
//tcp_client.c
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include<string.h>
#include<stdlib.h>
[Code].....
the above code works fine.if we copmile and run ./a.exe 192.xx.xx.xxx 1111 and press enter it works fine..everytime it asks "Please enter the message: " and if give that will be displayed in server. but my problem is i dont want to print everytime "Please enter the message: " i just want to feed some words one by one to the socket.
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Mar 30, 2009
im getting that error in my code for some reason. I compiled my code, and when i try to run this server it throws me an error on my call to setsocketopt(). The only way it can reach that part of my loop is if it succeeds when it calls sock() so I dont understand why the error says its an operation on a non-socket. Im just trying to set up a server to pass messages from a client to it a viceversa. Here is the code:
Code:
int main()
{
int socket_fd, new_socket_fd, k;
struct addrinfo hints, *server_info, *p;
struct sockaddr_storage peer_address;
code....
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Aug 1, 2010
I'm using gmake (v3.81) to build some c executables. As the first step in the process I run the files through a preprocessor (for embedded SQL). The preprocessor completes successfully, but the gmake reports an error and discontinues buiding the remaining dependencies...
make *** [myfile.c] Error 4
which (according to /usr/include/asm-generic/errno-base.h) means "interrupted System Call". My preprocessor doesn't raise any signals, so I'm not sure what's causing this error.
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Jun 23, 2010
I am facing the problem of calling cfitsio library from C program in linux. when i am givingthe option "gcc -o CreateLevel1DataFitsFile CreateLevel1DataFitsFile.c -lm -lcfitsio
"i am getting following error
/usr/lib/../lib/gcc/i386-redhat-linux/3.4.4/../../../libcfitsio.a(getcolj.o)(.text+0x7065):/backup/Astrosat/learning/cfits/cfitsio/getcolj.c:3098: more undefined references to `__xtoll' follow
[code]...
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Sep 11, 2014
I am developing a script to automate some database setup, but I have an issue I cannot figure out. I prompt for some input with whiptail and select a default if nothing is entered. However, if you do not enter anything, it normally returns 0, but this time it is returning an empty value.
Code: Select all # This one does work!
 # Set the source path
 TMPPATH=$(whiptail --backtitle "Linux Build Configuration"
  --title "Source-Code Path"
  --inputbox "Default: $SRCPATH" 0 60
  3>&2 2>&1 1>&3)
[Code] ....
So what is wrong with the second code?
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Feb 12, 2010
I have having some trouble working with wide characters, which is,
Sample code:
TCHAR fname[512];
_tcslcpy(fname, L"/root/Desktop/all/TheGrandTunnels.fgc", 512);
[code]...
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Jan 23, 2010
I've got a strange bug that I cannot figure out how to solve. Here is the function.
Code:
int getnexttab(char input[], int index, int length)
{
[code]....
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Mar 21, 2011
I have created an object where I pass a string and a long value to it <in Java>, currently I am adding the values to my Object so I can then add it to a list like so:
Code:
List myList;
ImageObject io;
for(i = 0; i < 10; i++)
[code]....
This is what the object currently looks like:
Code:
public final class ImageObject<name, time>
{
public String name = "";
public long time = 0;
[code]....
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