single Socket for listening and sending/receiving, Simultaneously?

This is a discussion on single Socket for listening and sending/receiving, Simultaneously? within the Networking/Device Communication forums, part of the General Programming Boards category; Hi, Is it possible to use the same network Socket simultaneously, for listening (for incoming connections) and communicating with a ...

  1. #1
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    Unhappy single Socket for listening and sending/receiving, Simultaneously?

    Hi,

    Is it possible to use the same network Socket simultaneously, for listening (for incoming connections) and communicating with a non-connected client (using the sendto() and recvfrom() functions)? Or must I have two separate sockets, and if so must the separate sockets also be bound to separate network ports? Just for the info, I am using WinSock 2 API functions.

    High thanks in advance
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  2. #2
    & the hat of GPL slaying Thantos's Avatar
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    If using accept() then you'll need two sockets. And yes they can both use the same port.

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    Yes I know... but is it possible to use the same listning socket for communication with a non-connected client simultaneously? In a multithread app for ex:

    * socket S is created.
    * bind S to network address with specific port.
    * Create thread T.
    * set S to listen for incoming connections.
    * meanwhile on thread T, socket S is sending and receiving messages.

    Is the above situation possible?
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  4. #4
    & the hat of GPL slaying Thantos's Avatar
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    I don't think so.

    However I think one of socket gurus should come answer it for sure.

  5. #5
    End Of Line Hammer's Avatar
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    How would you tell the difference between incoming data and a new connection request?
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

  6. #6
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    Lightbulb I think you need threads for this ...

    I think threads would be the right solution. I made a two-person chat application not too long ago, that I haven't finished yet, and I had to use threads, to control both sending and receiving data. Try going to http://msdn.microsoft.com/library and searching for _beginthread() or _beginthreadex(). I just used a function called Server(), declared as 'void Server()', that accepted connections and listened for incoming data. For multi-connection support is jus a little more complicated, but not by means of threads. You just have to create an array of listening sockets. For example:

    Code:
    // These are global variables
    SOCKET listening[10];       // Where ten is the maximum number of sockets that can be connected at once
    I don't know if this is EXACTLY what you need, but I think it should help you.

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    Originally posted by Hammer
    How would you tell the difference between incoming data and a new connection request?
    If it where possible, then the listening function would return when a connection is requested by another comp. And the incoming data would be returned from the receiving function. Although I don't know how it is handled on a low-level, it is probably up to the protocol used.


    Thanks for the info SyntaxBubble, it's not really what I was looking for but still useful. May I ask if you used threads that always listened for connections or message-based notification?
    We haven't inherited Earth from our parents; instead we have borrowed her from our children - old Indian saying.

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    I think this may be possible, but is strongly discouraged as you can run into all sorts of problems. It would be much better to use a completely seperate socket for listening whilst doing other i/o, and would make your code more readable & understandable.

  9. #9
    Carnivore ('-'v) Hunter2's Avatar
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    For multi-connection support is jus a little more complicated, but not by means of threads. You just have to create an array of listening sockets.
    Depending on what you mean, I may or may not disagree.

    Code:
    //Global variables
    SOCKET listening;
    (do something to bind it to a port and get it to listen)
    std::vector<SOCKET> clients;
    
    //In your thread procedure
    while(!quit)
    {
        clients.push_back(accept(listening, ...));
    }
    If you mean that in order to get more than 1 client to connect you need to create more listening sockets, I disagree. One listening socket can accept connections from any number of clients < the system's max number of sockets. If you mean that to get clients connecting on more than 1 port you need more listening sockets, I agree.
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    If you mean that to get clients connecting on more than 1 port you need more listening sockets, I agree.
    hello,

    I'm a newbie in c++. Anyway, do you have any idea on connecting clients thru different ports?

    I appreciate any help from you guys out there. thanks

  11. #11
    End Of Line Hammer's Avatar
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    Originally posted by rinin_farina
    hello,

    I'm a newbie in c++. Anyway, do you have any idea on connecting clients thru different ports?

    I appreciate any help from you guys out there. thanks
    Read through some of the tutorials mentioned in the "good links" thread.

    To get a client connecting on different ports, simply create more sockets and call connect on them. Obviously a server will need to be listening on each port you call to.
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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