Login or Register to Ask a Question and Join Our Community


Programming

Questions about sockets

Login to Discuss or Reply to this Discussion in Our Community

 
Thread Tools Search this Thread
Top Forums Programming Questions about sockets
# 1  
Old 10-24-2010
Questions about sockets
Hello,
the function listen creates a list that memorizes a number of incoming calls through a socket but how do the first call is deleted and the second becomes the first, is it done using accept?
I have read that accept can wait if it finds no calls in the listen list ,is it the same with read and write.I mean if i have used accept and use read while there is no write from the other side of the socket what will happen?If there was a write but not a read and again a write what will happen to the first string?Is the read function in a constant loop until it finds info to read?
# 2  
Old 10-24-2010
Quote:
Originally Posted by fireblast
Hello,
the function listen creates a list that memorizes a number of incoming calls through a socket but how do the first call is deleted and the second becomes the first, is it done using accept?
accept the first connection and immediately close it.
Quote:
I have read that accept can wait if it finds no calls in the listen list ,is it the same with read and write.
Yes. You can configure them as non-blocking, so they'll return error instead of making you wait, but they are blocking by default.
This User Gave Thanks to Corona688 For This Post:
fireblast
# 3  
Old 10-25-2010
I have another question , if i use sd=socket(...) on a process and i want to see this socket from an other process to use it in connect for example how can i do this?Is the variable holding the socket descriptor global ,i mean does every process see it once created?
# 4  
Old 10-25-2010
Quote:
Originally Posted by fireblast
I have another question , if i use sd=socket(...) on a process and i want to see this socket from an other process to use it in connect for example how can i do this?Is the variable holding the socket descriptor global ,i mean does every process see it once created?
No, file/socket descriptors are assigned on a per-process basis, so simply passing the descriptor to another process isn't possible. There are methods to do this, but they're more complicated than that - see this recent thread for hints.
This User Gave Thanks to JohnGraham For This Post:
fireblast
# 5  
Old 10-27-2010
I want to create a child process when there is a call in a socket ,how can i know if there is a least one process in the listen list to create the process so that i will not create needless processes?Does listen blocks the process if there are zero elements in the list?
Last edited by fireblast; 10-27-2010 at 11:01 AM..
# 6  
Old 10-27-2010
use select()
you should use select() to do what you want.

BSD sockets already optimizes this for you.

When you look at the file descriptor in the FD_SET, check if its the listening socket, if it is, then accept a new connection and do what you want.

Code:
 int sel = select(fdmax+1, &read_fds, NULL, NULL, &tv);
        
        if (sel == -1) {
            perror("select()");abort();
        } else if (sel) {
            // data must be ready
			
			for(i = 0; i <= fdmax; i++) {
				if (FD_ISSET(i, &read_fds)) {
					if (i == listening_sock) {
						/* handle a new connection */
						client_sock = accept(listening_sock, (struct sockaddr *) &client_sin, &addr_len);
						
						if (client_sock < 0) {perror("accept failed");abort();}
						FD_SET(client_sock, &master); /* add to master fd set */
						if (client_sock > fdmax) fdmax = client_sock; /* set max */
						
					} else {
						/* read data from client */
						read_bytes = recv(i, buffer, expected_data_len, 0);
						
						// do stuff with data from client
						
					} /* end read data from client */
				} /* end if FD_SET */
			} /* end loop through all fds */
		} /* end while loop */
		
	} else {
		// no data within tv.tv_sec seconds
		continue;
	}

# 7  
Old 11-05-2010
if i have a variable for example buf[10] and i then make a fork in the code if i change the buf variable in one process like buf="end" will the buf in the other process change too?
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. Programming

Any example about sockets in C++?

Hi, i am student, think learning about c++, someone has a example the how establish a conection with sockets :b::b: (1 Reply)
Discussion started by: mmartinez
1 Replies

2. Red Hat

Sockets

hai guys, I'm doing a project in which one server communicates with several clients. How can i do it when i have different port numbers???:confused: (0 Replies)
Discussion started by: rajeshb6
0 Replies

3. Programming

Help with sockets in C

if i have a server which wants to connect to exactly 5 clients, does that mean i need 5 socket file descriptors and use listen(socket_fd,1); for each one or just do listen(socket_fd,5) also whats the second parameter number mean? what happens if i put 0 there? also if i am connected... (28 Replies)
Discussion started by: omega666
28 Replies

4. Homework & Coursework Questions

Print questions from a questions folder in a sequential order

1.) I am to write scripts that will be phasetest folder in the home directory. 2.) The folder should have a set-up,phase and display files I have written a small script which i used to check for the existing users and their password. What I need help with: I have a set of questions in a... (19 Replies)
Discussion started by: moraks007
19 Replies

5. Programming

Sockets

Hi,i now moved into a different section where i need to use sockets. i am completely nill in sockets. can some body please provide me what are the requirements for a socket. to use sockets in c. thanks (1 Reply)
Discussion started by: MrUser
1 Replies

6. Programming

need help with sockets

anyone and teach me how to save standard output to a file in a client/server socket. I know how to read them to the screen but i'm not quite sure how to save them to a file. my read to screen file code: memset(line, 0x0, LINE_ARRAY_SIZE); while (recv(connectSocket, line, MAX_MSG, 0) >... (1 Reply)
Discussion started by: crunchyuser
1 Replies

7. Solaris

Sockets in use

Is there a way to see what sockets are in use? The developers here are getting some defunct processes and they would like to get a socket list. This is on a Solaris 8 machine. Thanks! (1 Reply)
Discussion started by: kjbaumann
1 Replies

8. UNIX for Dummies Questions & Answers

sockets

how do i mointor how many sockets are opened from a particular foriegn address? (2 Replies)
Discussion started by: kirpond
2 Replies

9. Programming

Sockets!?!?!?!?!?!

I am looking for a way to have a program listen on a port (example: 8000) for communication I will be sending via that port to it(Linux Kernel machine). Once it recieves an appropiate command I need it to run a .bat file in linux. I know what I need to do but I am running into a few problems:... (8 Replies)
Discussion started by: bigB8210
8 Replies

10. Programming

sockets...

Hi ! I had a verry simple question to ask... In unix when we create pipes.. the unnamed pipes that is... is there any way to access those pipes outside the code ? Another thing.. do sockets have an entry in the inode table ? TIA, Devyani. (1 Reply)
Discussion started by: devy8
1 Replies
Login or Register to Ask a Question