FBB::ServerSocket(3) Server socket accepting Internet connection requests


#include <bobcat/serversocket>
Linking option: -lbobcat


An FBB::ServerSocket may be constructed to listen for connection requests from the Internet or from the local host. Connection requests may be accepted in either blocking or non-blocking modes. When a connection is accepted a socket is returned which may be used to read information from or write information to the client that requested the connection. The socket that is made available is a file descriptor which may be used to initialize a std::istream and/or std::ostream. The std::istream is used to read information from the client process; the std::ostream is used to send information to the client process. Since a socket may be considered a file descriptor the available FBB::IFdStream, FBB::IFdStreamBuf, FBB::OFdStream, and FBB::OFdStreamBuf classes may be used profitably here. Note that having available a socket does not mean that this defines the communication protocol. It is (still) the responsibility of the programmer to comply with an existing protocol or to implement a tailor-made protocol. The latter situation implies that the sequence of input- and output operations is defined by the programmer.

A Unix Domain server socket can be defined using FBB::LocalServerSocket.


All constructors, members, operators and manipulators, mentioned in this man-page, are defined in the namespace FBB.




  • ServerSocket(size_t port):
    This constructor initializes an FBB::ServerSocket object, which will listen for connections at the specified port. The construction of the socket does not mean that the FBB::ServerSocket object is actually listening for connections. To start listening, the member listen() should be used. The copy constructor is not available.


All members of FBB::SocketBase (and thus of FBB::InetAddress) are available, as FBB::ServerSocket inherits from FBB::SocketBase.
  • void listen(size_t backlog = 5, bool blocking = true):
    The listen() member defines the way the FBB::ServerSocket will listen for clients requesting a connection. It can be used only once with a FBB::ServerSocket. An FBB::Exception object is thrown if listening fails, if the constructor could not create a socket, or if the SocketBase base class could not properly be constructed.
  • The listen() member's backlog parameter defines the size of the FBB::ServerSocket's internal queue in which connection requests may be stored waiting for their turn to be serviced. When backlog requests are waiting and another request arrives, then that request is lost.
  • The member's second parameter, blocking, is used to control the blocking mode. By default, blocking is used, and listen() will wait until a connection is established. This is ok in situations where clients connect infrquently and for relatively short time intervals. Otherwise, in more complex programs, an FBB::Selector object can be used to sense input on the server socket and/or on various client sockets.
  • SocketBase accept():
    The accept() member returns an FBB::SocketBase object containing information about the client whose connection request was accepted. The FBB::SocketBase object's socket value may be used to initialize streams that can be used to communicate with the client. In more complex programs the FBB::SocketBase could be passed to a class derived from FBB::Fork, handling the communication with the child as a separate (child) process.


See also the clientsocket(3bobcat) example.
    #include <iostream>
    #include <bobcat/serversocket>
    #include <bobcat/ifdstream>
    #include <bobcat/ofdstream>
    #include <bobcat/a2x>
    using namespace std;
    using namespace FBB;
    int main(int argc, char **argv)
        if (argc == 1)
            cerr << "Provide server port number\n";
            return 1;
        size_t portnr = A2x(argv[1]);
        ServerSocket server(portnr);
        cerr << "server listens on port " << argv[1] << endl;
        cerr << "serversocket returns:\n" <<
            "address = " << server.dottedDecimalAddress() << "\n"
            "port    = " << server.port() << endl;
        int fd = server.socket();       // open the socket's descriptor
        cout << "File descriptor of the socket is " << fd << "\n"
            "The server terminates when it receives a "
                                        "single `q' on a line\n"
            "A connection is terminated when no input "
                                        "is received anymore.\n"
            "Then another connection is possible" << endl;
        server.listen();                // listen in blocking mode
        while (true)
            SocketBase fdb = server.accept();
            int fd = fdb.socket();
            cerr << "Client FD = " << fd << ", " << endl <<
                    "address = " << fdb.dottedDecimalAddress() << ", " << 
                    endl <<
                    "communication through port " << fdb.port() << endl;
            IFdStream in(fd);           // stream to read from client
            OFdStream out(fd);          // stream to write to client
            string cmd;
            while (getline(in, cmd))
                cout << "Got: " << cmd << endl;
                out << "Got: " << cmd << "\r" << endl;
                if (cmd[0] == 'q')
                    return 0;
            cout << "Ready for another connection\n";
    catch (Exception const &err)
        cerr <<
            err.what() << endl <<
            "Server socket on port " << argv[1] << 
            " can't be opened" << endl;
        return -1;


bobcat/serversocket - defines the class interface


None Reported.


  • bobcat_4.02.00-x.dsc: detached signature;
  • bobcat_4.02.00-x.tar.gz: source archive;
  • bobcat_4.02.00-x_i386.changes: change log;
  • libbobcat1_4.02.00-x_*.deb: debian package holding the libraries;
  • libbobcat1-dev_4.02.00-x_*.deb: debian package holding the libraries, headers and manual pages;
  • http://sourceforge.net/projects/bobcat: public archive location;


Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.


This is free software, distributed under the terms of the GNU General Public License (GPL).


Frank B. Brokken ([email protected]).