I am connecting to port 7(echo service) in the remote machine.
suppose port 7 is not running in the remote machine I do not want to wait in connect call for long time.. so I am using non blocking connect with timeout of 3 seconds. But I am always getting the return code 1 from select call though the echo service is not running incase of write falgs set.
In the above FD_ISSET is returning true and when it tries to write it retrun EPIPE, because of not connected. How we decide that service is ready for writing?
I have client and server connected.
client write and read from csock.
server write and read from ssock
suppose the server does :
....
close(ssock); //send FIN to client
othertask();
....
READ ERROR
if after the server close() the client does:
...
read(csock,...);
...... (2 Replies)
I am presently refactoring a windows deamon with an eye towards porting it to linux someday.
Presently the application uses a single background thread and asynchronous socket I/O to implement FTP and HTTP clients in a single switch statement (2000 lines and 100 cases just for the switch... (3 Replies)
Hi Friends,
I have written a program which will listener for more than 1000 requests per second from a single socket descriptor and then it will process those requestes. Its taking X amount of time. Now i want to reduce that time. Will I can write multiple threads to receive the... (2 Replies)
Hi,
I was porting ipv4 application to ipv6; i was done with TCP transports. Now i am facing problem with SCTp transport at runtime.
To test SCTP transport I am using following server and client socket programs. Server program runs fine, but client program fails giving Invalid Arguments for... (0 Replies)
Why does this socket function only read the first 1440 chars of the stream. Why not the whole stream ? I checked it with gdm and valgrind and everything seems correct...
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include... (3 Replies)
Can anyone tell what happens if each end writes at the same time on the same socket ?
- if one of them issues a read() after write() has completed, will it record into the buffer what the other sent ?
ex.
e1 writes to e2 - - - while - - - e2 writes to e1 (at the same time)
e1 read () - what... (1 Reply)
I need clarification on whether it is okay to set socket options on a listening socket
simultaneously when it is being used in an accept() call?
Following is the scenario:-
-- Task 1 - is executing in a loop - polling a listen socket, lets call it 'fd', (whose file descriptor is global)... (2 Replies)
Hello all,
I have a requirement to read and write to a tcp socket from an HP-UX shell script. I see a /dev/tcp character device on my servers:
crw-rw-rw- 1 root root 72 0x00004f Mar 28 18:37 /dev/tcp
So I believe this is what I should use. The problem is that all the... (2 Replies)
will there be any unexpected results on looping connect call for a non blocking socket to determine the connection based on error code. I am getting connection unsuccessful intermittently and so wondering whether is the timeout 500 millisec not sufficient or looping connect cause any unexpected.
... (7 Replies)
among the below socket programming api's, please let me know which are blocking and non-blocking.
socket
accept
bind
listen
write
read
close (2 Replies)
Discussion started by: VSSajjan
2 Replies
LEARN ABOUT FREEBSD
fd_set
SELECT(2) BSD System Calls Manual SELECT(2)NAME
select -- synchronous I/O multiplexing
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/select.h>
int
select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);
FD_SET(fd, &fdset);
FD_CLR(fd, &fdset);
FD_ISSET(fd, &fdset);
FD_ZERO(&fdset);
DESCRIPTION
The select() system call examines the I/O descriptor sets whose addresses are passed in readfds, writefds, and exceptfds to see if some of
their descriptors are ready for reading, are ready for writing, or have an exceptional condition pending, respectively. The only exceptional
condition detectable is out-of-band data received on a socket. The first nfds descriptors are checked in each set; i.e., the descriptors
from 0 through nfds-1 in the descriptor sets are examined. On return, select() replaces the given descriptor sets with subsets consisting of
those descriptors that are ready for the requested operation. The select() system call returns the total number of ready descriptors in all
the sets.
The descriptor sets are stored as bit fields in arrays of integers. The following macros are provided for manipulating such descriptor sets:
FD_ZERO(&fdset) initializes a descriptor set fdset to the null set. FD_SET(fd, &fdset) includes a particular descriptor fd in fdset.
FD_CLR(fd, &fdset) removes fd from fdset. FD_ISSET(fd, &fdset) is non-zero if fd is a member of fdset, zero otherwise. The behavior of
these macros is undefined if a descriptor value is less than zero or greater than or equal to FD_SETSIZE, which is normally at least equal to
the maximum number of descriptors supported by the system.
If timeout is not a null pointer, it specifies the maximum interval to wait for the selection to complete. System activity can lengthen the
interval by an indeterminate amount.
If timeout is a null pointer, the select blocks indefinitely.
To effect a poll, the timeout argument should not be a null pointer, but it should point to a zero-valued timeval structure.
Any of readfds, writefds, and exceptfds may be given as null pointers if no descriptors are of interest.
RETURN VALUES
The select() system call returns the number of ready descriptors that are contained in the descriptor sets, or -1 if an error occurred. If
the time limit expires, select() returns 0. If select() returns with an error, including one due to an interrupted system call, the descrip-
tor sets will be unmodified.
ERRORS
An error return from select() indicates:
[EBADF] One of the descriptor sets specified an invalid descriptor.
[EFAULT] One of the arguments readfds, writefds, exceptfds, or timeout points to an invalid address.
[EINTR] A signal was delivered before the time limit expired and before any of the selected events occurred.
[EINVAL] The specified time limit is invalid. One of its components is negative or too large.
[EINVAL] The nfds argument was invalid.
SEE ALSO accept(2), connect(2), getdtablesize(2), gettimeofday(2), kqueue(2), poll(2), read(2), recv(2), send(2), write(2), clocks(7)NOTES
The default size of FD_SETSIZE is currently 1024. In order to accommodate programs which might potentially use a larger number of open files
with select(), it is possible to increase this size by having the program define FD_SETSIZE before the inclusion of any header which includes
<sys/types.h>.
If nfds is greater than the number of open files, select() is not guaranteed to examine the unused file descriptors. For historical reasons,
select() will always examine the first 256 descriptors.
STANDARDS
The select() system call and FD_CLR(), FD_ISSET(), FD_SET(), and FD_ZERO() macros conform with IEEE Std 1003.1-2001 (``POSIX.1'').
HISTORY
The select() system call appeared in 4.2BSD.
BUGS
Version 2 of the Single UNIX Specification (``SUSv2'') allows systems to modify the original timeout in place. Thus, it is unwise to assume
that the timeout value will be unmodified by the select() system call. FreeBSD does not modify the return value, which can cause problems
for applications ported from other systems.
BSD November 17, 2002 BSD