--- name: "serversocket" section: "3bobcat" platform: "linux" package: "libbobcat-dev" version: "6.07.01-2" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/serversocket" --- # serversocket(3bobcat) Server socket accepting Internet connection requests ## NAME FBB::ServerSocket - Server socket accepting Internet connection requests ## SYNOPSIS **#include \**\ 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 - o **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**. - o **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. - - o **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)](/clientsocket/3bobcat.md) example. ``` #include #include #include #include #include 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)](/bobcat/7.md), [**clientsocket**(3bobcat)](/clientsocket/3bobcat.md), [**fork**(3bobcat)](/fork/3bobcat.md), [**ifdstream**(3bobcat)](/ifdstream/3bobcat.md), [**ifdbuf**(3bobcat)](/ifdbuf/3bobcat.md), [**inetaddress**(3bobcat)](/inetaddress/3bobcat.md), [**localserversocket**(3bobcat)](/localserversocket/3bobcat.md), [**ofdstream**(3bobcat)](/ofdstream/3bobcat.md), [**ofdstream**(3bobcat)](/ofdstream/3bobcat.md), [**select**(2)](/select/2.md), [**selector**(3bobcat)](/selector/3bobcat.md), [**socketbase**(3bobcat)](/socketbase/3bobcat.md) ## BUGS None Reported. ## BOBCAT PROJECT FILES - o *https://fbb-git.gitlab.io/bobcat/*: gitlab project page; Debian Bobcat project files: - o *libbobcat6*: debian package containing the shared library, changelog and copyright note; - o *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**).