# FBB::LocalServerSocket(3bobcat)

## Unix Domain Server Socket
(libbobcat-dev_6.07.01)

## 2005-2025

## NAME

FBB::LocalServerSocket - Unix Domain Server socket accepting connection requests

## SYNOPSIS

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

## DESCRIPTION

An FBB::LocalServerSocket defines a Unix Domain server socket, listening for connection requests from the local host using a Unix Domain socket. 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 requesting 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.

## NAMESPACE

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

## INHERITS FROM

FBB::LocalSocketBase

## ENUMERATION

The following enumeration is defined in th class FBB::LocalServerSocket:

enum Socket
This enumeration holds two values:

- KEEP:
  When this value is specified at construction time, the file representing the Unix Domain Socket is not removed when the LocalServerSocket is destroyed.
- UNLINK:
  When this value is specified at construction time, the file representing the Unix Domain Socket is removed when the LocalServerSocket is destroyed. As a socket cannot be reused, this is the default value used with the LocalServerSocket constructor.

## CONSTRUCTOR

- LocalServerSocket():
  This constructor creates an empty (non-functioning) FBB::LocalServerSocket object. Before it can be used, the open() member must be called (see below).
- LocalServerSocket(string const &name, Socket action = UNLINK) throw (Exception):
  This constructor initializes an FBB::LocalServerSocket object, which will listen for connection requests using the named Unix Domain socket. An FBB::Exception is thrown if the socket could not be constructed. If the constructor is given a second argument FBB::LocalServerSocket::KEEP, the constructed socket is not unlinked when the FBB::LocalServerSocket object is destroyed. The construction of the socket does not mean that the FBB::LocalServerSocket object is actually listening for connections. To start listening, the member listen() should be called.

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

## MEMBER FUNCTIONS

- size_t accept():
  The accept() member returns an size_t which is a file descriptor (socket) that may be used to communicate with the client requesting the connection. In more complex programs the returned file descriptor (socket) could be passed to a class derived from FBB::Fork, handling the communication with the child as a separate (child) process.

- void listen(size_t backlog = 5, bool blocking = true):
  The listen() member defines the way the FBB::LocalServerSocket will listen for clients requesting a connection. It can be used only once with a FBB::LocalServerSocket. An FBB::Exception object is thrown if listening fails.

  The listen() member's backlog parameter defines the size of the FBB::LocalServerSocket'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.

- void open(string const &name, Socket action = UNLINK):
  This member prepares a FBB::LocalServerSocket object for use. It should only be used in combination with the default constructor. Following open() the FBB:::LocalServerSocket object will be able to listen for connection requests using the named Unix Domain socket. An FBB::Exception is thrown if the socket could not be constructed. If the a second argument FBB::LocalServerSocket::KEEP, is provided the constructed socket is not unlinked when the FBB::LocalServerSocket object is destroyed. The construction of the socket does not mean that the FBB::LocalServerSocket object is actually listening for connections. To start listening, the member listen() should be called next.

## EXAMPLE

See also the localclientsocket(3bobcat) example.

        #include <iostream>
        #include <bobcat/localserversocket>
        #include <bobcat/ifdstream>
        #include <bobcat/ofdstream>

        using namespace std;
        using namespace FBB;

        int main(int argc, char **argv)
        try
        {
            if (argc == 1)
            {
                cerr << "Provide local filename, e.g., /tmp/uds\n";
                return 1;
            }

            LocalServerSocket server(argv[1]);

            cerr << "server using `" << argv[1] << "'" << endl;

            cout <<
                "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)
            {
                int fd = server.accept();

                cerr << "Client FD = " << fd << ", " << 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), localclientsocket(3bobcat), fork(3bobcat), ifdstream(3bobcat), ifdbuf(3bobcat), localsocketbase(3bobcat), ofdstream(3bobcat), ofdstream(3bobcat), select(2), selector(3bobcat), serversocket(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).