CODEWITHSUNDEEP
socketsd
S. Jenson
S. Jenson

Reputation: 13

Assign session specific data to a socket

I'm writing a server application in D, who should be able to manage n connections simultaneously.

To achieve this i am using std.socket.Socket.select. This works fine. But I can't bind session specific data to the socket and i don't see any way to do this, cause Socket does not allow to save a handle to user specific data. After

Socket.select(socketSet, null, null);

I'm able to get all affected sockets, but I can't assign this sockets to my user specific session data. What's my mistake? Is it possible to reach my goal in this way? Or should I choose another way for my requirements?

My relevant code:

ushort port = 5010;
stoprequest = false;

auto listener = new TcpSocket();
assert(listener.isAlive);
listener.blocking = false;
listener.bind(new InternetAddress(port));
listener.listen(10);

enum MAX_CONNECTIONS = 100;
auto socketSet = new SocketSet(MAX_CONNECTIONS + 1);
Socket[] reads;
Session[] sessions;


while (true)
{
    socketSet.add(listener);

    foreach (session; sessions)
        socketSet.add(session.socket);

    Socket.select(socketSet, null, null);

    for (size_t i = 0; i < reads.length; i++)
    {

        if (socketSet.isSet(reads[i]))
        {
            // Now i should acces to session related data, but how?
            char[1024] buf;
            auto datLength = reads[i].receive(buf[]);

            if (datLength == Socket.ERROR)
                writeln("Connection error.");
            else if (datLength != 0)
            {
                writefln("Received %d bytes from %s: \"%s\"", datLength, reads[i].remoteAddress().toString(), buf[0..datLength]);
                continue;
            }
            else { // Error Handling. Shortened, since unimportant for the example}

            reads[i].close();

            reads = reads.remove(i);
            i--;
         }
    }

    if (socketSet.isSet(listener))
    {
        Socket sn = null;
        sn = listener.accept();

        if (reads.length < MAX_CONNECTIONS)
        {
            Session session = new Session();
            session.socket = sn;
            sessions ~= session;
        }
        else { // Error Handling for too many connection. Shortened, since unimportant for the example}}
    }

        socketSet.reset();
}

Upvotes: 0

Views: 77

Answers (2)

Adam D. Ruppe
Adam D. Ruppe

Reputation: 25605

A few other alternatives you can consider:

1) use a subclass of Socket. You can make your own class that inherits from it and adds more stuff.

2) The poll function is found in import core.sys.posix.poll;, and you can pass socket.handle to that as well. But note it will not work on Windows without modification.

or indeed 3) do your own lookup table, that works too.

Note that the std.socket.Socket is a very thin wrapper around the bsd socket api, just internally it does conveniently handle the slight differences between Windows and posix. Still it is pretty easy to adapt code to use the other apis with it (or tutorials on C language stuff to D) since it is all basically the same thing - and literally the same functions if you import core.sys stuff.

Upvotes: 0

S. Jenson
S. Jenson

Reputation: 13

The hint to use poll() was helpful. After reading https://daniel.haxx.se/docs/poll-vs-select.html I think that both variants work and neither of them are the real thing. For an efficient way, I should better deal with libev. Fortunately, efficiency is not my problem in this particular project. For this reason I will use select(), because i found out, that accessing handle gives me a unique number which can be passed to a own lookup table. This allows me to assign session data to a socket. So I prefer to stick with the encapsulated functionality of std.socket.Socket and don't work around it.

My concrete question can therefore be answered with :

Use Socket.handle to identify the socket and manage session related data

Upvotes: 1

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