# FBB::ServerSocket(3bobcat)

## Server Socket
(libbobcat-dev_6.14.00)

## 2005-2026

## NAME

FBB::ServerSocket - Server socket accepting Internet connection requests

## SYNOPSIS

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

## DESCRIPTION

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.

## NAMESPACE

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

## INHERITS FROM

FBB::SocketBase

## CONSTRUCTOR

- 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.

Copy and move constructors (and assignment operators) are not available.

## MEMBER FUNCTIONS

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.

## EXAMPLE

See also the clientsocket(3bobcat) example.

        #include <iostream>
        #include <string>
        #include <bobcat/serversocket>
        #include <bobcat/ifdstream>
        #include <bobcat/ofdstream>

        using namespace std;
        using namespace FBB;

        int main(int argc, char **argv)
        try
        {
            if (argc == 1)
            {
                cerr << "Provide server port number\n";
                return 1;
            }

            size_t portnr = stoul(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;
        }

## FILES

bobcat/serversocket - defines the class interface

## SEE ALSO

bobcat(7), clientsocket(3bobcat), fork(3bobcat), ifdstream(3bobcat), ifdbuf(3bobcat), inetaddress(3bobcat), localserversocket(3bobcat), ofdstream(3bobcat), ofdstream(3bobcat), select(2), selector(3bobcat), socketbase(3bobcat)

## BUGS

None Reported.

## BOBCAT PROJECT FILES

- https://fbb-git.gitlab.io/bobcat/: gitlab project page;

Debian Bobcat project files:

- libbobcat6: debian package containing the shared library, changelog and copyright note;
- libbobcat-dev: debian package containing the static library, headers, manual pages, and developer info;

## BOBCAT

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

## COPYRIGHT

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

## AUTHOR

Frank B. Brokken (f.b.brokken@rug.nl).