SocketClient (Apache Commons Net 3.6 API)

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:
SocketFactory

Field Summary

Fields
Modifier and Type	Field and Description
`protected int`	`_defaultPort_` The default port the client should connect to.
`protected String`	`_hostname_` The hostname used for the connection (null = no hostname supplied).
`protected InputStream`	`_input_` The socket's InputStream.
`protected OutputStream`	`_output_` The socket's OutputStream.
`protected ServerSocketFactory`	`_serverSocketFactory_` The socket's ServerSocket Factory.
`protected 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.
`protected int`	`connectTimeout`
`static String`	`NETASCII_EOL` The end of line character sequence used by most IETF protocols.

Constructor Summary

Constructors
Constructor and Description

SocketClient()
Default constructor for SocketClient.

Constructors
Constructor and Description
`SocketClient()` Default constructor for SocketClient.

Method Summary

Methods
Modifier and Type	Method and 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`	`addProtocolCommandListener(ProtocolCommandListener listener)` Adds a ProtocolCommandListener.
`void`	`connect(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(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(InetAddress host, int port, 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(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(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(String hostname, int port, 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.
`protected void`	`createCommandSupport()` Create the CommandSupport instance if required
`void`	`disconnect()` Disconnects the socket connection.
`protected void`	`fireCommandSent(String command, String message)` If there are any listeners, send them the command details.
`protected void`	`fireReplyReceived(int replyCode, String reply)` If there are any listeners, send them the reply details.
`Charset`	`getCharset()` Gets the charset.
`String`	`getCharsetName()` Deprecated. Since the code now requires Java 1.6 as a mininmum
`protected ProtocolCommandSupport`	`getCommandSupport()` Subclasses can override this if they need to provide their own instance field for backwards compatibilty.
`int`	`getConnectTimeout()` Get the underlying socket connection timeout.
`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.
`boolean`	`getKeepAlive()` Returns the current value of the SO_KEEPALIVE flag on the currently opened socket.
`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.
`Proxy`	`getProxy()` Gets the proxy for use with all the connections.
`protected int`	`getReceiveBufferSize()` Get the current receivedBuffer size
`InetAddress`	`getRemoteAddress()`
`int`	`getRemotePort()` Returns the port number of the remote host to which the client is connected.
`protected int`	`getSendBufferSize()` Get the current sendBuffer size
`ServerSocketFactory`	`getServerSocketFactory()` Get the underlying `ServerSocketFactory`
`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`	`isAvailable()` Make various checks on the socket to test if it is available for use.
`boolean`	`isConnected()` Returns true if the client is currently connected to a server.
`void`	`removeProtocolCommandListener(ProtocolCommandListener listener)` Removes a ProtocolCommandListener.
`void`	`setCharset(Charset charset)` Sets the charset.
`void`	`setConnectTimeout(int connectTimeout)` Sets the connection timeout in milliseconds, which will be passed to the `Socket` object's connect() method.
`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`	`setKeepAlive(boolean keepAlive)` Sets the SO_KEEPALIVE flag on the currently opened socket.
`void`	`setProxy(Proxy proxy)` Sets the proxy for use with all the connections.
`void`	`setReceiveBufferSize(int size)` Sets the underlying socket receive buffer size.
`void`	`setSendBufferSize(int size)` Set the underlying socket send buffer size.
`void`	`setServerSocketFactory(ServerSocketFactory factory)` Sets the ServerSocketFactory used by the SocketClient to open ServerSocket connections.
`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(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 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 Socket _socket_
```
    The socket used for the connection.
  - _hostname_
```
protected String _hostname_
```
    The hostname used for the connection (null = no hostname supplied).
  - _defaultPort_
```
protected int _defaultPort_
```
    The default port the client should connect to.
  - _input_
```
protected InputStream _input_
```
    The socket's InputStream.
  - _output_
```
protected OutputStream _output_
```
    The socket's OutputStream.
  - _socketFactory_
```
protected SocketFactory _socketFactory_
```
    The socket's SocketFactory.
  - _serverSocketFactory_
```
protected ServerSocketFactory _serverSocketFactory_
```
    The socket's ServerSocket Factory.
  - connectTimeout
```
protected int connectTimeout
```
- Constructor Detail
  - 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 Detail
  - _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 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:
    
    IOException - (SocketException) if a problem occurs with the socket
  - 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(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(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,
           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.
  - 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(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.
  - 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 - If there is an error closing the socket.
  - 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.
  - 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:
    NET-350
  - 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 SocketException
```
    Set 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
  - setSendBufferSize
```
public void setSendBufferSize(int size)
                       throws SocketException
```
    Set 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
  - getSendBufferSize
```
protected int getSendBufferSize()
```
    Get the current sendBuffer size
    
    Returns:
    the size, or -1 if not initialised
    Since:
    
    3.0
  - 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
  - getReceiveBufferSize
```
protected int getReceiveBufferSize()
```
    Get the current receivedBuffer size
    
    Returns:
    the size, or -1 if not initialised
    Since:
    
    3.0
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - 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
  - verifyRemote
```
public boolean verifyRemote(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.
    
    Parameters:
    socket - the item to check against
    
    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). Any proxy setting is discarded.
    
    Parameters:
    factory - The new SocketFactory the SocketClient should use.
  - 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
  - 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
  - getConnectTimeout
```
public int getConnectTimeout()
```
    Get the underlying socket connection timeout.
    
    Returns:
    timeout (in ms)
    Since:
    
    2.0
  - getServerSocketFactory
```
public ServerSocketFactory getServerSocketFactory()
```
    Get the underlying ServerSocketFactory
    
    Returns:
    The server socket factory
    Since:
    
    2.2
  - addProtocolCommandListener
```
public void addProtocolCommandListener(ProtocolCommandListener listener)
```
    Adds a ProtocolCommandListener.
    
    Parameters:
    listener - The ProtocolCommandListener to add.
    Since:
    
    3.0
  - removeProtocolCommandListener
```
public void removeProtocolCommandListener(ProtocolCommandListener listener)
```
    Removes a ProtocolCommandListener.
    
    Parameters:
    listener - The ProtocolCommandListener to remove.
    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
  - 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
  - createCommandSupport
```
protected void createCommandSupport()
```
    Create the CommandSupport instance if required
  - getCommandSupport
```
protected ProtocolCommandSupport getCommandSupport()
```
    Subclasses can override this if they need to provide their own instance field for backwards compatibilty.
    
    Returns:
    the CommandSupport instance, may be null
    Since:
    
    3.0
  - 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
  - getProxy
```
public Proxy getProxy()
```
    Gets the proxy for use with all the connections.
    
    Returns:
    the current proxy for connections.
  - getCharsetName
```
@Deprecated
public String getCharsetName()
```
    Deprecated. Since the code now requires Java 1.6 as a mininmum
    
    Gets the charset name.
    
    Returns:
    the charset.
    Since:
    
    3.3
  - getCharset
```
public Charset getCharset()
```
    Gets the charset.
    
    Returns:
    the charset.
    Since:
    
    3.3
  - setCharset
```
public void setCharset(Charset charset)
```
    Sets the charset.
    
    Parameters:
    charset - the charset.
    Since:
    
    3.3

Class SocketClient

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NETASCII_EOL

_timeout_

_socket_

_hostname_

_defaultPort_

_input_

_output_

_socketFactory_

_serverSocketFactory_

connectTimeout

Constructor Detail

SocketClient

Method Detail

_connectAction_

connect

connect

connect

connect

connect

connect

disconnect

isConnected

isAvailable

setDefaultPort

getDefaultPort

setDefaultTimeout

getDefaultTimeout

setSoTimeout

setSendBufferSize

getSendBufferSize

setReceiveBufferSize

getReceiveBufferSize

getSoTimeout

setTcpNoDelay

getTcpNoDelay

setKeepAlive

getKeepAlive

setSoLinger

getSoLinger

getLocalPort

getLocalAddress

getRemotePort

getRemoteAddress

verifyRemote

setSocketFactory

setServerSocketFactory

setConnectTimeout

getConnectTimeout

getServerSocketFactory

addProtocolCommandListener

removeProtocolCommandListener

fireReplyReceived

fireCommandSent

createCommandSupport

getCommandSupport

setProxy

getProxy

getCharsetName

getCharset

setCharset