Package org.apache.commons.net

Class SocketClient

java.lang.Object
org.apache.commons.net.SocketClient
Direct Known Subclasses:
CharGenTCPClient, DaytimeTCPClient, DiscardTCPClient, FingerClient, FTP, IMAP, NNTP, POP3, RExecClient, SMTP, TelnetClient, TimeTCPClient
public abstract class SocketClient extends 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 instantiating 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.
See Also:

  • Field Details

  • Constructor Details

    • SocketClient

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

  • Method Details

    • _connectAction_

      protected void _connectAction_() throws 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 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:
      IOException - (SocketException) if a problem occurs with the socket

    • addProtocolCommandListener

      public void addProtocolCommandListener(ProtocolCommandListener listener)
      Adds a ProtocolCommandListener.
      Parameters:
      listener - The ProtocolCommandListener to add.
      Since:
      3.0

    • applySocketAttributes

      protected void applySocketAttributes() throws SocketException
      Applies socket attributes.
      Throws:
      SocketException - if there is an error in the underlying protocol, such as a TCP error.
      Since:
      3.8.0

    • checkOpenOutputStream

      protected OutputStream checkOpenOutputStream()
      Gets the non-null OutputStream or throws NullPointerException.

      This method does not allocate resources.

      Returns:
      the non-null OutputStream.
      Since:
      3.11.0

    • connect

      public void connect(InetAddress host) throws SocketException, 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:
      SocketException - If the socket timeout could not be set.
      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(InetAddress host, int port) throws SocketException, 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:
      SocketException - If the socket timeout could not be set.
      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(InetAddress host, int port, InetAddress localAddr, int localPort) throws SocketException, 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:
      SocketException - If the socket timeout could not be set.
      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(String hostname) throws SocketException, 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:
      SocketException - If the socket timeout could not be set.
      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(String hostname, int port) throws SocketException, 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:
      SocketException - If the socket timeout could not be set.
      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(String hostname, int port, InetAddress localAddr, int localPort) throws SocketException, 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:
      SocketException - If the socket timeout could not be set.
      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.

    • createCommandSupport

      protected void createCommandSupport()
      Create the CommandSupport instance if required

    • disconnect

      public void disconnect() throws 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:
      IOException - not thrown, subclasses may throw.

    • fireCommandSent

      protected void fireCommandSent(String command, String message)
      If there are any listeners, send them the command details.
      Parameters:
      command - the command name
      message - the complete message, including command name
      Since:
      3.0

    • fireReplyReceived

      protected void fireReplyReceived(int replyCode, String reply)
      If there are any listeners, send them the reply details.
      Parameters:
      replyCode - the code extracted from the reply
      reply - the full reply text
      Since:
      3.0

    • getCharset

      public Charset getCharset()
      Gets the charset.
      Returns:
      the charset.
      Since:
      3.3

    • getCharsetName

      @Deprecated public String getCharsetName()
      Deprecated.
      Since the code now requires Java 1.6 as a minimum
      Gets the charset name.
      Returns:
      the charset.
      Since:
      3.3

    • getCommandSupport

      protected ProtocolCommandSupport getCommandSupport()
      Subclasses can override this if they need to provide their own instance field for backwards compatibility.
      Returns:
      the CommandSupport instance, may be null
      Since:
      3.0

    • getConnectTimeout

      public int getConnectTimeout()
      Gets the underlying socket connection timeout.
      Returns:
      timeout (in ms)
      Since:
      2.0

    • getDefaultPort

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

    • 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.

    • getKeepAlive

      public boolean getKeepAlive() throws SocketException
      Returns the current value of the SO_KEEPALIVE flag on the currently opened socket. Delegates to Socket.getKeepAlive()
      Returns:
      True if SO_KEEPALIVE is enabled.
      Throws:
      SocketException - if there is a problem with the socket
      NullPointerException - if the socket is not currently open
      Since:
      2.2

    • getLocalAddress

      public InetAddress getLocalAddress()
      Returns the local address to which the client's socket is bound. Delegates to Socket.getLocalAddress()
      Returns:
      The local address to which the client's socket is bound.
      Throws:
      NullPointerException - if the socket is not currently open

    • getLocalPort

      public int getLocalPort()
      Returns the port number of the open socket on the local host used for the connection. Delegates to Socket.getLocalPort()
      Returns:
      The port number of the open socket on the local host used for the connection.
      Throws:
      NullPointerException - if the socket is not currently open

    • getProxy

      public Proxy getProxy()
      Gets the proxy for use with all the connections.
      Returns:
      the current proxy for connections.

    • getReceiveBufferSize

      protected int getReceiveBufferSize()
      Gets the current receivedBuffer size
      Returns:
      the size, or -1 if not initialized
      Since:
      3.0

    • getRemoteAddress

      public InetAddress getRemoteAddress()
      Returns:
      The remote address to which the client is connected. Delegates to Socket.getInetAddress()
      Throws:
      NullPointerException - if the socket is not currently open

    • getRemoteInetSocketAddress

      protected InetSocketAddress getRemoteInetSocketAddress()
      Gets the remote socket address used for the connection.
      Returns:
      the remote socket address used for the connection
      Since:
      3.10.0

    • getRemotePort

      public int getRemotePort()
      Returns the port number of the remote host to which the client is connected. Delegates to Socket.getPort()
      Returns:
      The port number of the remote host to which the client is connected.
      Throws:
      NullPointerException - if the socket is not currently open

    • getSendBufferSize

      protected int getSendBufferSize()
      Gets the current sendBuffer size
      Returns:
      the size, or -1 if not initialized
      Since:
      3.0

    • getServerSocketFactory

      public ServerSocketFactory getServerSocketFactory()
      Gets the underlying ServerSocketFactory
      Returns:
      The server socket factory
      Since:
      2.2

    • getSoLinger

      public int getSoLinger() throws 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:
      SocketException - If the operation fails.
      NullPointerException - if the socket is not currently open

    • getSoTimeout

      public int getSoTimeout() throws SocketException
      Returns the timeout in milliseconds of the currently opened socket.
      Returns:
      The timeout in milliseconds of the currently opened socket.
      Throws:
      SocketException - If the operation fails.
      NullPointerException - if the socket is not currently open

    • getTcpNoDelay

      public boolean getTcpNoDelay() throws 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:
      SocketException - If the operation fails.
      NullPointerException - if the socket is not currently open

    • isAvailable

      public boolean isAvailable()
      Make various checks on the socket to test if it is available for use. Note that the only sure test is to use it, but these checks may help in some cases.
      Returns:
      true if the socket appears to be available for use
      Since:
      3.0
      See Also:

    • isConnected

      public boolean isConnected()
      Returns true if the client is currently connected to a server. Delegates to Socket.isConnected()
      Returns:
      True if the client is currently connected to a server, false otherwise.

    • removeProtocolCommandListener

      public void removeProtocolCommandListener(ProtocolCommandListener listener)
      Removes a ProtocolCommandListener.
      Parameters:
      listener - The ProtocolCommandListener to remove.
      Since:
      3.0

    • setCharset

      public void setCharset(Charset charset)
      Sets the charset.
      Parameters:
      charset - the charset.
      Since:
      3.3

    • setConnectTimeout

      public void setConnectTimeout(int connectTimeout)
      Sets the connection timeout in milliseconds, which will be passed to the Socket object's connect() method.
      Parameters:
      connectTimeout - The connection timeout to use (in ms)
      Since:
      2.0

    • 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.

    • setDefaultTimeout

      public void setDefaultTimeout(int timeout)
      Sets 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 the currently opened socket. _timeout_ contains the new timeout value.
      Parameters:
      timeout - The timeout in milliseconds to use for the socket connection.

    • setKeepAlive

      public void setKeepAlive(boolean keepAlive) throws SocketException
      Sets the SO_KEEPALIVE flag on the currently opened socket. From the Javadocs, the default keepalive time is 2 hours (although this is implementation dependent). It looks as though the Windows WSA sockets implementation allows a specific keepalive value to be set, although this seems not to be the case on other systems.
      Parameters:
      keepAlive - If true, keepAlive is turned on
      Throws:
      SocketException - if there is a problem with the socket
      NullPointerException - if the socket is not currently open
      Since:
      2.2

    • setProxy

      public void setProxy(Proxy proxy)
      Sets the proxy for use with all the connections. The proxy is used for connections established after the call to this method.
      Parameters:
      proxy - the new proxy for connections.
      Since:
      3.2

    • setReceiveBufferSize

      public void setReceiveBufferSize(int size) throws SocketException
      Sets the underlying socket receive buffer size.
      Parameters:
      size - The size of the buffer in bytes.
      Throws:
      SocketException - never (but subclasses may wish to do so)
      Since:
      2.0

    • setSendBufferSize

      public void setSendBufferSize(int size) throws SocketException
      Sets the underlying socket send buffer size.
      Parameters:
      size - The size of the buffer in bytes.
      Throws:
      SocketException - never thrown, but subclasses might want to do so
      Since:
      2.0

    • setServerSocketFactory

      public void setServerSocketFactory(ServerSocketFactory factory)
      Sets the ServerSocketFactory used by the SocketClient to open ServerSocket 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 ServerSocketFactory the SocketClient should use.
      Since:
      2.0

    • 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). Any proxy setting is discarded.
      Parameters:
      factory - The new SocketFactory the SocketClient should use.

    • setSoLinger

      public void setSoLinger(boolean on, int val) throws 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:
      SocketException - If the operation fails.
      NullPointerException - if the socket is not currently open

    • setSoTimeout

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

      To set the initial timeout, use setDefaultTimeout(int) instead.

      Parameters:
      timeout - The timeout in milliseconds to use for the currently open socket connection.
      Throws:
      SocketException - If the operation fails.
      NullPointerException - if the socket is not currently open

    • setTcpNoDelay

      public void setTcpNoDelay(boolean on) throws 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:
      SocketException - If the operation fails.
      NullPointerException - if the socket is not currently open

    • verifyRemote

      public boolean verifyRemote(Socket socket)
      Verifies that the remote end of the given socket is connected to 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.
      Parameters:
      socket - the item to check against
      Returns:
      True if the remote hosts are the same, false if not.