Class SocketClient

  • Direct Known Subclasses:
    CharGenTCPClient, DaytimeTCPClient, DiscardTCPClient, FingerClient, NNTP, POP3, RExecClient, SMTP, TelnetClient, TimeTCPClient

    public abstract class SocketClient
    extends java.lang.Object
    The SocketClient provides the basic operations that are required of client objects accessing sockets. It is meant to be subclassed to avoid having to rewrite the same code over and over again to open a socket, close a socket, set timeouts, etc. Of special note is the setSocketFactory method, which allows you to control the type of Socket the SocketClient creates for initiating network connections. This is especially useful for adding SSL or proxy support as well as better support for applets. For example, you could create a SocketFactory that requests browser security capabilities before creating a socket. All classes derived from SocketClient should use the _socketFactory_ member variable to create Socket and ServerSocket instances rather than instanting them by directly invoking a constructor. By honoring this contract you guarantee that a user will always be able to provide his own Socket implementations by substituting his own SocketFactory.
    Author:
    Daniel F. Savarese
    See Also:
    SocketFactory
    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected int _defaultPort_
      The default port the client should connect to.
      protected java.io.InputStream _input_
      The socket's InputStream.
      protected boolean _isConnected_
      A status variable indicating if the client's socket is currently open.
      protected java.io.OutputStream _output_
      The socket's OutputStream.
      protected java.net.Socket _socket_
      The socket used for the connection.
      protected SocketFactory _socketFactory_
      The socket's SocketFactory.
      protected int _timeout_
      The timeout to use after opening a socket.
      static java.lang.String NETASCII_EOL
      The end of line character sequence used by most IETF protocols.
    • Constructor Summary

      Constructors 
      Constructor Description
      SocketClient()
      Default constructor for SocketClient.
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void _connectAction_()
      Because there are so many connect() methods, the _connectAction_() method is provided as a means of performing some action immediately after establishing a connection, rather than reimplementing all of the connect() methods.
      void connect​(java.lang.String hostname)
      Opens a Socket connected to a remote host at the current default port and originating from the current host at a system assigned port.
      void connect​(java.lang.String hostname, int port)
      Opens a Socket connected to a remote host at the specified port and originating from the current host at a system assigned port.
      void connect​(java.lang.String hostname, int port, java.net.InetAddress localAddr, int localPort)
      Opens a Socket connected to a remote host at the specified port and originating from the specified local address and port.
      void connect​(java.net.InetAddress host)
      Opens a Socket connected to a remote host at the current default port and originating from the current host at a system assigned port.
      void connect​(java.net.InetAddress host, int port)
      Opens a Socket connected to a remote host at the specified port and originating from the current host at a system assigned port.
      void connect​(java.net.InetAddress host, int port, java.net.InetAddress localAddr, int localPort)
      Opens a Socket connected to a remote host at the specified port and originating from the specified local address and port.
      void disconnect()
      Disconnects the socket connection.
      int getDefaultPort()
      Returns the current value of the default port (stored in _defaultPort_ ).
      int getDefaultTimeout()
      Returns the default timeout in milliseconds that is used when opening a socket.
      java.net.InetAddress getLocalAddress()
      Returns the local address to which the client's socket is bound.
      int getLocalPort()
      Returns the port number of the open socket on the local host used for the connection.
      java.net.InetAddress getRemoteAddress()  
      int getRemotePort()
      Returns the port number of the remote host to which the client is connected.
      int getSoLinger()
      Returns the current SO_LINGER timeout of the currently opened socket.
      int getSoTimeout()
      Returns the timeout in milliseconds of the currently opened socket.
      boolean getTcpNoDelay()
      Returns true if Nagle's algorithm is enabled on the currently opened socket.
      boolean isConnected()
      Returns true if the client is currently connected to a server.
      void setDefaultPort​(int port)
      Sets the default port the SocketClient should connect to when a port is not specified.
      void setDefaultTimeout​(int timeout)
      Set the default timeout in milliseconds to use when opening a socket.
      void setSocketFactory​(SocketFactory factory)
      Sets the SocketFactory used by the SocketClient to open socket connections.
      void setSoLinger​(boolean on, int val)
      Sets the SO_LINGER timeout on the currently opened socket.
      void setSoTimeout​(int timeout)
      Set the timeout in milliseconds of a currently open connection.
      void setTcpNoDelay​(boolean on)
      Enables or disables the Nagle's algorithm (TCP_NODELAY) on the currently opened socket.
      boolean verifyRemote​(java.net.Socket socket)
      Verifies that the remote end of the given socket is connected to the the same host that the SocketClient is currently connected to.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • NETASCII_EOL

        public static final java.lang.String NETASCII_EOL
        The end of line character sequence used by most IETF protocols. That is a carriage return followed by a newline: "\r\n"
        See Also:
        Constant Field Values
      • _timeout_

        protected int _timeout_
        The timeout to use after opening a socket.
      • _socket_

        protected java.net.Socket _socket_
        The socket used for the connection.
      • _isConnected_

        protected boolean _isConnected_
        A status variable indicating if the client's socket is currently open.
      • _defaultPort_

        protected int _defaultPort_
        The default port the client should connect to.
      • _input_

        protected java.io.InputStream _input_
        The socket's InputStream.
      • _output_

        protected java.io.OutputStream _output_
        The socket's OutputStream.
      • _socketFactory_

        protected SocketFactory _socketFactory_
        The socket's SocketFactory.
    • Constructor Detail

      • SocketClient

        public SocketClient()
        Default constructor for SocketClient. Initializes _socket_ to null, _timeout_ to 0, _defaultPort to 0, _isConnected_ to false, and _socketFactory_ to a shared instance of DefaultSocketFactory.
    • Method Detail

      • _connectAction_

        protected void _connectAction_()
                                throws java.io.IOException
        Because there are so many connect() methods, the _connectAction_() method is provided as a means of performing some action immediately after establishing a connection, rather than reimplementing all of the connect() methods. The last action performed by every connect() method after opening a socket is to call this method.

        This method sets the timeout on the just opened socket to the default timeout set by setDefaultTimeout() , sets _input_ and _output_ to the socket's InputStream and OutputStream respectively, and sets _isConnected_ to true.

        Subclasses overriding this method should start by calling super._connectAction_() first to ensure the initialization of the aforementioned protected variables.

        Throws:
        java.io.IOException
      • connect

        public void connect​(java.net.InetAddress host,
                            int port)
                     throws java.net.SocketException,
                            java.io.IOException
        Opens a Socket connected to a remote host at the specified port and originating from the current host at a system assigned port. Before returning, _connectAction_() is called to perform connection initialization actions.

        Parameters:
        host - The remote host.
        port - The port to connect to on the remote host.
        Throws:
        java.net.SocketException - If the socket timeout could not be set.
        java.io.IOException - If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
      • connect

        public void connect​(java.lang.String hostname,
                            int port)
                     throws java.net.SocketException,
                            java.io.IOException
        Opens a Socket connected to a remote host at the specified port and originating from the current host at a system assigned port. Before returning, _connectAction_() is called to perform connection initialization actions.

        Parameters:
        hostname - The name of the remote host.
        port - The port to connect to on the remote host.
        Throws:
        java.net.SocketException - If the socket timeout could not be set.
        java.io.IOException - If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
        UnknownHostException - If the hostname cannot be resolved.
      • connect

        public void connect​(java.net.InetAddress host,
                            int port,
                            java.net.InetAddress localAddr,
                            int localPort)
                     throws java.net.SocketException,
                            java.io.IOException
        Opens a Socket connected to a remote host at the specified port and originating from the specified local address and port. Before returning, _connectAction_() is called to perform connection initialization actions.

        Parameters:
        host - The remote host.
        port - The port to connect to on the remote host.
        localAddr - The local address to use.
        localPort - The local port to use.
        Throws:
        java.net.SocketException - If the socket timeout could not be set.
        java.io.IOException - If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
      • connect

        public void connect​(java.lang.String hostname,
                            int port,
                            java.net.InetAddress localAddr,
                            int localPort)
                     throws java.net.SocketException,
                            java.io.IOException
        Opens a Socket connected to a remote host at the specified port and originating from the specified local address and port. Before returning, _connectAction_() is called to perform connection initialization actions.

        Parameters:
        hostname - The name of the remote host.
        port - The port to connect to on the remote host.
        localAddr - The local address to use.
        localPort - The local port to use.
        Throws:
        java.net.SocketException - If the socket timeout could not be set.
        java.io.IOException - If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
        UnknownHostException - If the hostname cannot be resolved.
      • connect

        public void connect​(java.net.InetAddress host)
                     throws java.net.SocketException,
                            java.io.IOException
        Opens a Socket connected to a remote host at the current default port and originating from the current host at a system assigned port. Before returning, _connectAction_() is called to perform connection initialization actions.

        Parameters:
        host - The remote host.
        Throws:
        java.net.SocketException - If the socket timeout could not be set.
        java.io.IOException - If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
      • connect

        public void connect​(java.lang.String hostname)
                     throws java.net.SocketException,
                            java.io.IOException
        Opens a Socket connected to a remote host at the current default port and originating from the current host at a system assigned port. Before returning, _connectAction_() is called to perform connection initialization actions.

        Parameters:
        hostname - The name of the remote host.
        Throws:
        java.net.SocketException - If the socket timeout could not be set.
        java.io.IOException - If the socket could not be opened. In most cases you will only want to catch IOException since SocketException is derived from it.
        UnknownHostException - If the hostname cannot be resolved.
      • disconnect

        public void disconnect()
                        throws java.io.IOException
        Disconnects the socket connection. You should call this method after you've finished using the class instance and also before you call connect() again. _isConnected_ is set to false, _socket_ is set to null, _input_ is set to null, and _output_ is set to null.

        Throws:
        java.io.IOException - If there is an error closing the socket.
      • isConnected

        public boolean isConnected()
        Returns true if the client is currently connected to a server.

        Returns:
        True if the client is currently connected to a server, false otherwise.
      • setDefaultPort

        public void setDefaultPort​(int port)
        Sets the default port the SocketClient should connect to when a port is not specified. The _defaultPort_ variable stores this value. If never set, the default port is equal to zero.

        Parameters:
        port - The default port to set.
      • getDefaultPort

        public int getDefaultPort()
        Returns the current value of the default port (stored in _defaultPort_ ).

        Returns:
        The current value of the default port.
      • setDefaultTimeout

        public void setDefaultTimeout​(int timeout)
        Set the default timeout in milliseconds to use when opening a socket. This value is only used previous to a call to connect() and should not be confused with setSoTimeout() which operates on an the currently opened socket. _timeout_ contains the new timeout value.

        Parameters:
        timeout - The timeout in milliseconds to use for the socket connection.
      • getDefaultTimeout

        public int getDefaultTimeout()
        Returns the default timeout in milliseconds that is used when opening a socket.

        Returns:
        The default timeout in milliseconds that is used when opening a socket.
      • setSoTimeout

        public void setSoTimeout​(int timeout)
                          throws java.net.SocketException
        Set the timeout in milliseconds of a currently open connection. Only call this method after a connection has been opened by connect().

        Parameters:
        timeout - The timeout in milliseconds to use for the currently open socket connection.
        Throws:
        java.net.SocketException - If the operation fails.
      • getSoTimeout

        public int getSoTimeout()
                         throws java.net.SocketException
        Returns the timeout in milliseconds of the currently opened socket.

        Returns:
        The timeout in milliseconds of the currently opened socket.
        Throws:
        java.net.SocketException - If the operation fails.
      • setTcpNoDelay

        public void setTcpNoDelay​(boolean on)
                           throws java.net.SocketException
        Enables or disables the Nagle's algorithm (TCP_NODELAY) on the currently opened socket.

        Parameters:
        on - True if Nagle's algorithm is to be enabled, false if not.
        Throws:
        java.net.SocketException - If the operation fails.
      • getTcpNoDelay

        public boolean getTcpNoDelay()
                              throws java.net.SocketException
        Returns true if Nagle's algorithm is enabled on the currently opened socket.

        Returns:
        True if Nagle's algorithm is enabled on the currently opened socket, false otherwise.
        Throws:
        java.net.SocketException - If the operation fails.
      • setSoLinger

        public void setSoLinger​(boolean on,
                                int val)
                         throws java.net.SocketException
        Sets the SO_LINGER timeout on the currently opened socket.

        Parameters:
        on - True if linger is to be enabled, false if not.
        val - The linger timeout (in hundredths of a second?)
        Throws:
        java.net.SocketException - If the operation fails.
      • getSoLinger

        public int getSoLinger()
                        throws java.net.SocketException
        Returns the current SO_LINGER timeout of the currently opened socket.

        Returns:
        The current SO_LINGER timeout. If SO_LINGER is disabled returns -1.
        Throws:
        java.net.SocketException - If the operation fails.
      • getLocalPort

        public int getLocalPort()
        Returns the port number of the open socket on the local host used for the connection.

        Returns:
        The port number of the open socket on the local host used for the connection.
      • getLocalAddress

        public java.net.InetAddress getLocalAddress()
        Returns the local address to which the client's socket is bound.

        Returns:
        The local address to which the client's socket is bound.
      • getRemotePort

        public int getRemotePort()
        Returns the port number of the remote host to which the client is connected.

        Returns:
        The port number of the remote host to which the client is connected.
      • getRemoteAddress

        public java.net.InetAddress getRemoteAddress()
        Returns:
        The remote address to which the client is connected.
      • verifyRemote

        public boolean verifyRemote​(java.net.Socket socket)
        Verifies that the remote end of the given socket is connected to the the same host that the SocketClient is currently connected to. This is useful for doing a quick security check when a client needs to accept a connection from a server, such as an FTP data connection or a BSD R command standard error stream.

        Returns:
        True if the remote hosts are the same, false if not.
      • setSocketFactory

        public void setSocketFactory​(SocketFactory factory)
        Sets the SocketFactory used by the SocketClient to open socket connections. If the factory value is null, then a default factory is used (only do this to reset the factory after having previously altered it).

        Parameters:
        factory - The new SocketFactory the SocketClient should use.