org.apache.commons.net

Class SocketClient

java.lang.Object
|
+--org.apache.commons.net.SocketClient

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

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

Field Summary

static String	NETASCII_EOL The end of line character sequence used by most IETF protocols.
int	_defaultPort_ The default port the client should connect to.
InputStream	_input_ The socket's InputStream.
boolean	_isConnected_ A status variable indicating if the client's socket is currently open.
OutputStream	_output_ The socket's OutputStream.
SocketFactory	_socketFactory_ The socket's SocketFactory.
Socket	_socket_ The socket used for the connection.
int	_timeout_ The timeout to use after opening a socket.

Constructor Summary

SocketClient()

Default constructor for SocketClient.

Method Summary

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(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(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(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, 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(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(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	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.
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.
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	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	setSocketFactory(SocketFactory factory) Sets the SocketFactory used by the SocketClient to open socket connections.
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.

Field Details

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"

_defaultPort_

protected int _defaultPort_

The default port the client should connect to.

_input_

protected InputStream _input_

The socket's InputStream.

_isConnected_

protected boolean _isConnected_

A status variable indicating if the client's socket is currently open.

_output_

protected OutputStream _output_

The socket's OutputStream.

_socketFactory_

protected SocketFactory _socketFactory_

The socket's SocketFactory.

_socket_

protected Socket _socket_

The socket used for the connection.

_timeout_

protected int _timeout_

The timeout to use after opening a socket.

Constructor Details

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 Details

_connectAction_

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. 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.

connect

public 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. Before returning, _connectAction_() is called to perform connection initialization actions.

Parameters:

host - The remote host.

Throws:

- If the socket timeout could not be set.
- If the socket could not be opened.

connect

public 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. 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:

- If the socket timeout could not be set.
- If the socket could not be opened.

connect

public 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. 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:

- If the socket timeout could not be set.
- If the socket could not be opened.

connect

public void connect(String hostname)

Parameters:

hostname - The name of the remote host.

Throws:

- If the socket timeout could not be set.
- If the socket could not be opened.
- If the hostname cannot be resolved.

connect

public void connect(String hostname, int port)

Parameters:

hostname - The name of the remote host.
port - The port to connect to on the remote host.

Throws:

- If the socket timeout could not be set.
- If the socket could not be opened.
- If the hostname cannot be resolved.

connect

public void connect(String hostname, int port, InetAddress localAddr, int localPort)

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:

- If the socket timeout could not be set.
- If the socket could not be opened.
- If the hostname cannot be resolved.

disconnect

public void disconnect()

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:

- If there is an error closing the socket.

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.

getLocalAddress

public 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.

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.

getRemoteAddress

public InetAddress getRemoteAddress()

Returns:

The remote address to which the client is connected.

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.

getSoLinger

public int getSoLinger()

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:

- If the operation fails.

getSoTimeout

public int getSoTimeout()

Returns the timeout in milliseconds of the currently opened socket.

Returns:

The timeout in milliseconds of the currently opened socket.

Throws:

- If the operation fails.

getTcpNoDelay

public boolean getTcpNoDelay()

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:

- If the operation fails.

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.

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.

setSoLinger

public void setSoLinger(boolean on, int val)

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:

- If the operation fails.

setSoTimeout

public void setSoTimeout(int timeout)

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:

- If the operation fails.

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.

setTcpNoDelay

public void setTcpNoDelay(boolean on)

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:

- If the operation fails.

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

Returns:

True if the remote hosts are the same, false if not.