[Webinar] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

UDP - recvfrom() call

Posted on 2000-04-04
7
Medium Priority
?
485 Views
Last Modified: 2008-03-17
There are two simple programs: A, and B communicating through UDP (socket() called with SOCK_DGRAM). A just bounces all datagrams.
B sends a datagram to A, calls recvfrom and then
examines the sockaddr *from field.

Depedning on:
a) sockaddr_in declaration or allocation
b) recvfrom calling point
c) B's compilation host
I'm getting different results:

Compiled on my machine (RH 6.1):

sockaddr_in  | recvfrom()     | result
-----------------------------
main()          | main()           | A's address
answer0()     | answer0()      | EINVAL
B.c              | answer1()      | 0.0.0.0
malloc()        | answer2()     | EINVAL

Compiled on my university host:

sockaddr_in  | recvfrom()     | result
--------------------------
main()          | main()           | A's address
answer0()     | answer0()      | 0.0.0.0
B.c              | answer1()      | 0.0.0.0
malloc()        | answer2()     | 0.0.0.0

I don't like the idea of putting all my code
in main(), so hope there's someone who has
at least the slightest idea about what's going
on and how to make it work. I'll provide any
additional information, if it is necessary.

Sources of A and B are here: http://rainbow.mimuw.edu.pl/~robson/AB.tgz 
0
Comment
Question by:Robson
  • 4
  • 3
7 Comments
 
LVL 2

Expert Comment

by:munsie
ID: 2685755
the code would be very helpful, if you don't mind... i have a few ideas, but I would like to see what A and B are doing.

thanks,
dennis
0
 
LVL 4

Author Comment

by:Robson
ID: 2686743
I've put sources of A and B at http://rainbow.mimuw.edu.pl/~robson/AB.tgz
0
 
LVL 4

Author Comment

by:Robson
ID: 2686751
Edited text of question.
0
Transaction-level recovery for Oracle database

Veeam Explore for Oracle delivers low RTOs and RPOs with agentless transaction log backup and transaction-level recovery of Oracle databases. You can restore the database to a precise point in time, even to a specific transaction.

 
LVL 2

Accepted Solution

by:
munsie earned 1200 total points
ID: 2687360
in your get_answer2() routine, you didn't set the length field to be the sizeof(answer).  Actually, you didn't do this in multiple places...

set length before calling recvfrom() will fix your problem.

good luck,
dennis
0
 
LVL 4

Author Comment

by:Robson
ID: 2687763
Thank's a lot, dennis!
This requirement isn't mentioned either in man page, nor in Steven's book (I 've nearly broken its cover in anger). Also in example programs given by my network-programming teacher (he's going to score some, too) initialization isn't made.

Last, but not least:
I MISSED GREAT SCI-FI CONVENTION BECAUSE OF THIS EFFING BUG!
0
 
LVL 2

Expert Comment

by:munsie
ID: 2687971
glad it helped... sorry about the sci-fi convention, though

dennis
0
 
LVL 4

Author Comment

by:Robson
ID: 2688162
NOTE: I was wrong about Stevens' "Un*x Network Programming" - it explains this problem. I promise to read it carefully and with respect - and no more violence, of course :-).  
0

Featured Post

Windows Server 2016: All you need to know

Learn about Hyper-V features that increase functionality and usability of Microsoft Windows Server 2016. Also, throughout this eBook, you’ll find some basic PowerShell examples that will help you leverage the scripts in your environments!

Question has a verified solution.

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

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 demonstrate how we can upgrade Python from version 2.7.6 to Python 2.7.10 on the Linux Mint operating system. I am using an Oracle Virtual Box where I have installed Linux Mint operating system version 17.2. Once yo…
Exchange organizations may use the Journaling Agent of the Transport Service to archive messages going through Exchange. However, if the Transport Service is integrated with some email content management application (such as an anti-spam), the admin…
We’ve all felt that sense of false security before—locking down external access to a database or component and feeling like we’ve done all we need to do to secure company data. But that feeling is fleeting. Attacks these days can happen in many w…
Suggested Courses

865 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