🚀 go-pugleaf

In article <1993Jan26.222115.28187@slate.mines.colorado.edu>, iarit@slate.mines.colorado.edu (ARIT ISMAIL) writes:
|> Hi,
|> 
|> I don't know if this is the right place to post this, but
|> I need some help about writing a simple client/server program.
|> 
|> Here is what I am trying to do;
|> 
|> I want to write a program that will accept connections from
|> other programs and will communicate with them without forking.
|> I don't want to fork because the info should be generated on one
|> program, send to server and the server has to respond to every
|> program connected with the same info( if I fork, how  can I transfer
|> that info to child?).
|> 
|>   main                     main
|>   client <--> server <--> client
|>                 |
|>                 |
|>          _______________________________
|>          |         |        |        |
|>          v         v        v        v
|>        client1  client2  client3     ......
|> 
|> (main clients generate the info)
|> I know this is not an easy thing to do, but actually, I am having
|> problems with accept(..);
|> can I do something like this;
|> 
|> while(1)
|> {
|>  check_new_connection(); /* how can I check if there is any new
|> connection
|>                            without waiting, as far as I know accept(..)
|>                            blocks you 'till you get some connection*/
|>  check_clients();       /* I can do these, no problem. read if there is
|>                            any new info */
|>  if(thereIsNewInfo)
|>    inform_clients();     /* if I can create a list of handles for clients
|>                            this is no big deal */
|> 
|> }
|> My problem is getting new connections without waiting.
	If your problem is only about having a non-blocking "accept()", then
you mark the socket as non-blocking. If you then try accept() , you will see
that accept will accept the connection, if there is a pending connection request.
On the other hand if no pending connections are there, then accept 
will return immediately with an error (I think EWOULDBLOCK).
You can use fcntl (O_NDELAY or O_NONBLOCK) for the server socket to get this
feature.

|> 
|> I appreciate any help.
|> 
|> iarit@slate.mines.colorado.edu
-raj
1/27/93

In article <1993Jan26.222115.28187@slate.mines.colorado.edu>, iarit@slate.mines.colorado.edu (ARIT ISMAIL) writes:
|> Hi,
Hi.
|> 
|> I don't know if this is the right place to post this, but
|> I need some help about writing a simple client/server program.

Comp.unix.questions is usually a better forum for 
questions of this level.  I also highly recommend 
getting W. Richard Stevens' Unix_Network_Programming, 
which is an excellent reference with a large amount of
robust source code included.  The book is the best networking
reference I have seen.  It will be a well-spent $50.

|> 
|> Here is what I am trying to do;
|> 
|> I want to write a program that will accept connections from
|> other programs and will communicate with them without forking.
|> I don't want to fork because the info should be generated on one
|> program, send to server and the server has to respond to every
|> program connected with the same info( if I fork, how  can I transfer
|> that info to child?).

Shared memory. Sockets. Pipes.  Man pages are:

shmctl (2)              - shared memory control operations
shmget (2)              - get shared memory segment identifier
shmop, shmat, shmdt (2) - shared memory operations

for shared memory,

socket(2), connect(2), et al. for sockets, and 

pipe (2V)               - create an interprocess communication channel
popen, pclose (3S)      - open or close a pipe (for I/O) from or to a process

for pipes.  These three are common and reasonably portable. 

|> 
|> while(1)
|> {
|>  check_new_connection(); /* how can I check if there is any new
|> connection
|>                            without waiting, as far as I know accept(..)
|>                            blocks you 'till you get some connection*/
|>  check_clients();       /* I can do these, no problem. read if there is
|>                            any new info */
|>  if(thereIsNewInfo)
|>    inform_clients();     /* if I can create a list of handles for clients
|>                            this is no big deal */
|> 
|> }
|> My problem is getting new connections without waiting.

To get new connections without waiting, you can set the socket to
be non-blocking using the ioctl or fnctl calls, like so:

#include <sys/ioctl.h>
#include <errno.h>

char foo=(char) 1;

if (ioctl(sockfd, FIONBIO, &foo  ) < 0)
	printf("Error setting socket %d with code: %d", sockfd, errno);

The third argument is a char * which is expected to point
to the argument to ioctl; arg needs merely to be non-zero in
this case to set nonblocking IO for sockfd.

|> 
|> I appreciate any help.
|> 
|> iarit@slate.mines.colorado.edu

Anytime.
-jg
-- 
/*  Jeremy Gaffney [jg@cs.brown.edu gaffer@brownvm.brown.edu] */