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I've been following Beej's Guide to network programming, (which is really great) and when implementing
his streaming socket server ( <a href="http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#simpleserver">http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#simpleserver</a>[<a href="http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html#simpleserver" target="_blank" title="New Window">^</a>] )
it works just fine. To test it I opened a Konsole (using Kubuntu) and ran:
<code>
pacific@mainbox $ telnet localhost 3490
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Hello, world!Connection closed by foreign host.
</code>
However, when trying to make a class out of the above code, as shown below, I get a "accept: Bad file descriptor" error, repeatedly.
Not sure if these two functions (which are not part of the class) have anything to do with it:
void sigchld_handler(int s);
void *get_in_addr(struct sockaddr *sa);
Help on this would be much appreciated !!
Gvanto
Sources also here: <a href="http://www.sharedigest.com/socketserver.tar.gz">http://www.sharedigest.com/socketserver.tar.gz</a>[<a href="http://www.sharedigest.com/socketserver.tar.gz" target="_blank" title="New Window">^</a>]
main (WLFeeder.cpp):
<code>
#include <iostream>
#include <cstdlib>
#include <stdio.h>
#include <string>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include "SocketServer.h"
#define DO_MAIN 1
using namespace std;
using namespace wlns;
#ifdef DO_MAIN
int main(int argc, char *argv[]) {
SocketServer *s = new SocketServer();
if( s->initAddrInfo() != SUCCESS ) {
cout << "Error initializing address " << endl;
exit(1);
}
if( s->initBind() != SUCCESS ) {
cout << "Error initializing bind " << endl;
exit(1);
}
if( s->initListen() != SUCCESS ) {
cout << "Error initializing listen " << endl;
exit(1);
}
if( s->clearDeadProcesses() != SUCCESS ) {
cout << "Error clearing dead processes " << endl;
exit(1);
}
if( s->listenForConnections() != SUCCESS ) {
cout << "Error in listening for connections " << endl;
exit(1);
}
return 0;
}
#endif
</code>
SocketServer.h:
<code>
/*
* SocketServer.h
*
* Created on: 11/02/2009
* Author: pacific
*
* Generic, extendable socket-managing class handling
* network communications via sockets
*/
#ifndef SOCKETSERVER_H_
#define SOCKETSERVER_H_
#include <iostream>
#include <cstdlib>
#include <stdio.h>
#include <string>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#define BACKLOG 10 //no. of pending connections the queue will hold
#define PORT "3490"
using namespace std;
namespace wlns {
static int SUCCESS = 1;
static int FAILURE = 0;
class SocketServer {
private:
int sockfd_, new_fd_; //listen on sock_fd_, new connection on new_fd_
struct addrinfo hints_, *servinfo_, *p_; //hints and actual address
struct sockaddr_storage their_addr_; //connector's address information
socklen_t sin_size_;
struct sigaction sa_;
int yes_;
char s_[INET6_ADDRSTRLEN];
int rv_;
//char *remote_host_, *remote_port_;
public:
SocketServer();
virtual ~SocketServer();
int setLocalPort(char *lp);
char *getLocalPort();
int initAddrInfo();
int initBind();
int initListen();
int clearDeadProcesses();
int listenForConnections();
// int getSocketFileDescriptor();
// int setRemoteHostAndPort(char *host, char *port);
// int connectToRemoteHost();
};
}
#endif /* SOCKETSERVER_H_ */
</code>
SocketServer.cpp:
<code>
/*
* SocketServer.cpp
*
* Created on: 11/02/2009
* Author: pacific
*/
#include "SocketServer.h"
using namespace std;
namespace wlns {
void sigchld_handler(int s)
{
while(waitpid(-1, NULL, WNOHANG) > 0);
}
// 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);
}
SocketServer::SocketServer() {
yes_ = 1;
memset(&hints_, 0, sizeof hints_);
hints_.ai_family = AF_UNSPEC;
hints_.ai_socktype = SOCK_STREAM;
hints_.ai_flags = AI_PASSIVE; //bind to IP of the host we're running on, p148 Beej's
}
SocketServer::~SocketServer() {
// TODO Auto-generated destructor stub
}
/**
* Populates servinfo with the appropriate
*/
int SocketServer::initAddrInfo() {
cout << "initAddrInfo() :: Initializing address ..." << endl;
if( (rv_ = getaddrinfo(NULL, PORT, &hints_, &servinfo_)) == -1 ) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv_));
return FAILURE;
}
return SUCCESS;
}
int SocketServer::initBind() {
cout << "bindFirstPossible() :: ..." << endl;
for(p_ = servinfo_; p_ != NULL; p_ = p_->ai_next) {
if( (sockfd_ = socket(p_->ai_family, p_->ai_socktype, p_->ai_protocol)) == -1) {
perror("server: socket");
continue;
}
if( setsockopt(sockfd_, SOL_SOCKET, SO_REUSEADDR, &yes_, sizeof(int)) == -1 ) {
perror("setsockopt");
return FAILURE;
}
if (bind(sockfd_, p_->ai_addr, p_->ai_addrlen) == -1) {
close(sockfd_);
perror("server: bind");
continue;
}
break;
}
freeaddrinfo(servinfo_); //done with this struct
if(p_ == NULL) {
fprintf(stderr, "server failed to bind\n");
return FAILURE;
}
return SUCCESS;
}
int SocketServer::initListen() {
cout << "initListen() :: ..." << endl;
if( listen(sockfd_, BACKLOG) == -1 ) {
perror("listen");
return FAILURE;
}
return SUCCESS;
}
int SocketServer::clearDeadProcesses() {
cout << "clearDeadProcesses() :: ..." << endl;
sa_.sa_handler = sigchld_handler; //assign function pointer - not sure if it matters if its not a class method ?
sigemptyset(&sa_.sa_mask);
sa_.sa_flags = SA_RESTART;
if (sigaction(SIGCHLD, &sa_, NULL) == -1) {
perror("sigaction");
return FAILURE;
}
return SUCCESS;
}
int SocketServer::listenForConnections() {
cout << "listenForConnections() :: Listening..." << endl;
int rc = SUCCESS;
while(1) {
sin_size_ = sizeof their_addr_;
cout << "waiting to accept " << endl;
new_fd_ = accept(sockfd_, (struct sockaddr *)&their_addr_, &sin_size_);
if(new_fd_ == -1) {
perror("accept");
rc = FAILURE;
continue;
}
inet_ntop(their_addr_.ss_family, get_in_addr((struct sockaddr *)&their_addr_), s_, sizeof s_);
printf("SocketServer: got connection from %s\n", s_);
if(!fork()) { //this is child process
close(sockfd_);
if (send(new_fd_, "Hello, world!", 13, 0) == -1) {
perror("send");
rc = FAILURE;
}
close(new_fd_);
}
close(new_fd_); //parent doesnt need this
}
return rc;
}
} //end ns
</code>
OUTPUT:
<code>
pacific@mainbox /workspace/WLFeeder/Debug$ ./WLFeeder
initAddrInfo() :: Initializing address ...
bindFirstPossible() :: ...
initListen() :: ...
clearDeadProcesses() :: ...
listenForConnections() :: Listening...
waiting to accept //Here I entered the telnet command again, in a seperate Konsole terminal ...
SocketServer: got connection from ::ffff:127.0.0.1 //works once
waiting to accept
accept: Bad file descriptor // then keeps giving errors ...
waiting to accept
accept: Bad file descriptor
waiting to accept
accept: Bad file descriptor
waiting to accept
accept: Bad file descriptor
waiting to accept
</code>
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The one thing I notice is that your forked process doesn't exit (unlike the equivalent code in Beej's guide)?
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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Thanks a million Stuart, that did it !
I thought exit(0) was only to exit from a main routine or something,
did not realize it would exit from the if( ) { } routine ...
Gvanto
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gvanto wrote: exit(0) was only to exit from a main routine or something
No, it exits the current process - of course, which process is 'current' can get confusing with *nix, as the fork function creates a new process by duplicating the caller, so you have to track the two code paths, the parent process (where fork returns the child PID) and the child process (wehere fork returns zero).
In some ways it's easier to work with than Win32's CreateProcess, in other ways not.
Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p
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Ah ic, yeah that's what kind of got me I think. Not quite got the hang of these socket processes (and I'm pretty new to C++)
so still got a way to go. and a loooooooooong way before I start coding c++ in windows ! 
Thanks again for the help Stuart, much appreciated !
Best,
gvanto
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hi all,
can anybody help me build an application having multilingual support using VC++.
thanks!!
Varun Bhatt
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Check this[^]
-Sarath.
"Great hopes make everything great possible" - Benjamin Franklin
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Thanks a lot Sarath,
but i had already tried this and lots of other examples on code project and codeguru.com and on various other sites but not really useful to get an clear idea about how to do this.
THough, now i have an obscure idea about the steps but can you tell me the stepwise procedure to proceed. i was trying the following example
ddj.com/184404314?pgno=1
but atlast it resulted the following error
d:\varun\mltest\mltest\mltest.h(10) : fatal error C1083: Cannot open include file: 'MLDLL\resource.h': No such file or directory
MLTestDlg.cpp
d:\varun\mltest\mltest\mltest.h(10) : fatal error C1083: Cannot open include file: 'MLDLL\resource.h': No such file or directory
i have tried a lot to solve this but failed, can you suggest any solution?
Varun Bhatt
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Get the ML directory and files for your project and put it under current path of the workspace or in any include paths and compile.
-Sarath.
"Great hopes make everything great possible" - Benjamin Franklin
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Hi All,
---------------------
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---------------------
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---------------------
I need a splitter window (4 way) as shown above. I use the code
m_wndSplitter.CreateStatic(this, 1, 2));
m_wndSplitter1.CreateStatic(&m_wndSplitter,2,1,WS_CHILD |WS_VISIBLE, m_wndSplitter.IdFromRowCol (0, 0));
m_wndSplitter1.CreateView(0, 0, RUNTIME_CLASS(CLabel), CSize(250, 15), pContext) ;
m_wndSplitter1.CreateView(1, 0, RUNTIME_CLASS(CLView), CSize(250, 500), pContext) ;
m_wndSplitter2.CreateStatic(&m_wndSplitter,2,1,WS_CHILD |WS_VISIBLE, m_wndSplitter.IdFromRowCol (0, 1));
m_wndSplitter2.CreateView(0, 0, RUNTIME_CLASS(CLabel), CSize(250, 15), pContext) ;
m_wndSplitter2.CreateView(1, 0, RUNTIME_CLASS(CLView), CSize(250, 500), pContext) ;
But i got this
---------------------
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---------------------
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---------------------
I know that m_wndSplitter.CreateStatic(this, 2, 2));
is possible for this 4 way splittering.
But here wndSplitter1 & wndSplitter2 are the object of different splitter classes
Help me..
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You have to call m_wndSplitter.CreateView before calling .CreateStatic on the other splitters even though you will never use those views.
«_Superman_»
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Wow!! it works well.Thank u very much 
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Dears,
I have a doubt about the type casting in CString and LPCTSTR.
Please see the below code.
void FnWithArgs( LPCTSTR lpctstrBuffer )
{
// Do nothing;
}
void FnTest()
{
CString csBuffer;
FnWithArgs( csBuffer.operator LPCTSTR()); // Casting-1
FnWithArgs( static_cast<<LPCTSTR>>( csBuffer )); // Casting-2
}
In the code we can see that two casting methods are done.
My doubt is that which of the above ( Casting-1 or Casting-2 ) is better?
Actually I need the reason also.
Regards,
Krishnakumar
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They are the same. Casting-2 will internally be converted to Casting-1 before execution.
«_Superman_»
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«_Superman_» wrote: They are the same. Casting-2 will internally be converted to Casting-1 before execution.
Which one I can prefer?
Casting-1?
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Casting-2 is the standard.
So go with that.
«_Superman_»
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Thanks...
Regards,
Krishnakumar
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I think it's not necessary to type cast because the operator LPCTSTR() is not explicit. Just directly pass it.
-Sarath.
"Great hopes make everything great possible" - Benjamin Franklin
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hi, i have been trying to create a sqlite database using visual c++.
I'm getting an unfamiliar error message box while the program execute insert sql statement.I have posted the error message below. Please help me to solve this problem.
Thank you.
---------------------------------------------------------------------------------------------------------
Unhandled exception at 0x00000000 in sparta1.exe: 0xC0000005: Access violation reading location 0x000000v00.
the error message also have a break,continue and ignore button below the message box.
---------------------------------------------------------------------------------------------------------
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This is an informative message meaning that there was some exception (in lay mans term, it's like a malfunction) that was not handled in the code. The second chance exception does not really mean that there may be an error only in your code. Usually the code 0xc0000005 indicates a second chance exception. Did you try and debug your code to check the cause of the problem?
Are you aware of what exceptions are and why do they arise?
If not, go and read about exception to better understand the problem and then try to resolve it.
You need to google first, if you have "It's urgent please" mentioned in your question.
 _AnShUmAn_
modified on Thursday, February 12, 2009 12:25 AM
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Check all your pointers for errors.
This error is likely to be an uninitialized pointer or a pointer holding a wrong address.
«_Superman_»
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vanishaa wrote: I'm getting an unfamiliar error message box
Wow, if it's unfamiliar tp you, either you are very new to programming or you were programming quite good from the begining. Because I remember when I started programming, I got this kind of message a looooot of times.
Anyway, as other have suggested, this error is because you are trying to read a bad pointer. Use your debugger to locate the problem and use breakpoints before the crash to check if all your variables are initialized properly.
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Hi All
How can i remove duplicate item from list control?I have a list control report view which have 100 data.I want to reomve duplicate data(data which is present more than one time in list control).Plz help me
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How about comparing the items in the list control and checking if a copy of it exists?
If affirmative, use CListCtrl::DeleteItem...
Is your problem with the comparison part of the items or the removal of copies of data?
You need to google first, if you have "It's urgent please" mentioned in your question.
_AnShUmAn_
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