Question about sockets

Posted on 2006-11-02
Last Modified: 2010-04-22
Hello i have a program that uses a tcp socket to connect to a server, i want to send packets using that socket but from another program, i've tryed opening the socket file descriptor listed in /proc/<pid>/fd but that didn't worked for sockets (it worked on normal files). Is there a way to do this?
Question by:zionz

Expert Comment

ID: 17863830
look in <sys/socket.h> for the send function
it just might do the trick for ya
man 2 send
LVL 43

Expert Comment

ID: 17864657
Sorry - there's no way to take over file descriptor of another process(open file or socket).
opening /proc/PID/fd/number opens new instance of file in fact (it's symlink).
OK - there is possibility to transfer opened file descriptor from one process to another, but they have to cooperate(process have to be willing to give it's opened socket to another) - can they in Your example?

Expert Comment

ID: 17865304

A simple way is to fork your process and as the child-process you can communicate with parent-process over sockets.

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

LVL 34

Accepted Solution

Duncan Roe earned 250 total points
ID: 17871257
The /proc symbolic link for a socket looks like:
   lrwx------  1 dunc users 64 2006-10-21 10:31 10 -> socket:[1225]
When you try to open it, it fails:
   10:54:37$ cat 10
   cat: 10: No such device or address
It really is the open() call that fails (from strace):
   open("10", O_RDONLY|O_LARGEFILE)        = -1 ENXIO (No such device or address)
If the fd is a symlink to a real file then of course it works.

You need to modify the program that has the socket with the server. Make sure the socket fd has close_on_exec flag *not* set. Now any program you fork and exec has access to the socket. Any recieved data item can only be recieved by one process - the other misses out. So there needs to be co-operation in that regard.
LVL 43

Expert Comment

ID: 18044607
since no input from author: delete/no refund.
LVL 34

Expert Comment

by:Duncan Roe
ID: 18048631
Is that the rule?
LVL 34

Expert Comment

by:Duncan Roe
ID: 18048639
I mean, if it was the rule then Venabili  could just have recommened it straight off
LVL 43

Expert Comment

ID: 18051868
duncan_roe: what You want? It's just my suggestion. If You have another, bring it here.

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
why should double free() crash? 7 35
Equivalent solution for gettimezoneinformation 12 142
Installing rpm without root access 1 64
null coming in rpm name 3 79
Have you ever been frustrated by having to click seven times in order to retrieve a small bit of information from the web, always the same seven clicks, scrolling down and down until you reach your target? When you know the benefits of the command l…
The purpose of this article is to fix the unknown display problem in Linux Mint operating system. After installing the OS if you see Display monitor is not recognized then we can install "MESA" utilities to fix this problem or we can install additio…
In a recent question ( here at Experts Exchange, a member asked how to run an AutoHotkey script (.AHK) directly from Notepad++ (aka NPP). This video…
I've attached the XLSM Excel spreadsheet I used in the video and also text files containing the macros used below.…

730 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question