Sockets can be connected or unconnected. Unconnected sockets are produced by the socket() call. An unconnected socket can become a connected socket by:

• Client application: Actively connecting to another socket, using the connect() call

• Server application: Binding a name to the socket, and then listening for and accepting a connection from another socket, using the listen() and accept() calls.

Stream sockets require a connection before you can transfer data. Other types of sockets, such as datagram sockets, need not establish connections before use.