de.frame4j.net

Class ClientLil

java.lang.Object

de.frame4j.net.ClientLil

@MinDoc(copyright="Copyright 2005, 2014  A. Weinert",
        author="Albrecht Weinert",
        version="V.65",
        lastModified="3.06.2024",
        usage="start as Java application (-? for help)",
        purpose="a small IP client")
public class ClientLil
extends Object

Base for a TCP/IP client.

An object of this class is a tiny (wee) client. For a given server host and TCP port a point to point (P2P-) connection can be handled and multiply opened and re-used.

A short exchange initiated by this client is supported:
n* (client sends, server responds), client closes.

Basically the size and functionality of the client is not limited. An object of this class is also the base for the minimum useful client functionality — hence "ClientLil" (Scottish diminutiv).

Usage of ClientLil may look so:

   import de.frame4j.net.ClientLil;
   // ......
    
     ClientLil eventClientLil = new ClientLil();
     String   eventHost;
     int      eventPort;
     int      timeout;
     String   eventText;
    
   // .......
  
    
     if (eventClientLil == null) try {
        eventClientLil.setHost(eventHost); 
        eventClientLil.setPort(eventPort); 
        eventClientLil.setTimeOut(tiemOut); 
        eventClientLil.connect(true);  
     } catch (Exception e) {
        log.println("  ///   warning : event server " + eventHost
                      + " : " + e);
     }

     // while (.......
    
      String answ  = null;
      Exception ex = null;
      try {
        answ = eventClientLil.use(eventText); 
        /// ..... eventClientLil.use(...... 
        eventClientLil.disconnect();
      } catch (Exception e) { ex = e; }
      log.println("\n   /// eventserver < " + eventText
                + "\n   /// answered    > " + answ 
                + "\n   /// problems    : " + ex + "\n");
    

As test client for this class is also an application. For usage see:
java de.frame4j.net.ClientLil -?
java de.frame4j.net.ClientLil -en -?

Examples:
java de.frame4j.net.ClientLil pd310s -p 7 "try the echo"
java de.frame4j.net.ClientLil -telnet 192.168.89.33 -v


© Copyright 2002 - 2007, 2012 Albrecht Weinert

Version:

65 (3.06.2024)

Author:

Albrecht Weinert

Field Summary

Fields

Modifier and Type	Field and Description
protected String	encoding Encoding for textual input and output.
protected String	host The server's (the host's) name.
protected InetAddress	inetAddress The host address.
int	noOfAccIncMess The number of messages (still) to be accepted from server.
protected int	port The server's (the host's) port.
Socket	sock The socket.
InputStream	sockIn The socket input stream.
OutputStream	sockOut The socket output stream.
BufferedReader	sockReader The socket input as Reader.
PrintWriter	sockWriter The socket output as Writer.
protected int	timeOut Maximum wait time for the server's (host's) responses.

Constructor Summary

Constructors

Constructor and Description
ClientLil()

Method Summary

Modifier and Type	Method and Description
Socket	connect(boolean textIO) Connecting.
void	disconnect() Disconnecting.
String	getEncoding() Encoding for textual input and output.
String	getHost() The server's (the host's) name.
String	getHostAddress() The host address (as String).
int	getPort() The server's (the host's) port.
int	getTimeOut() Maximum wait time for the server's (host's) responses.
static void	main(String[] args) The ClientLil (wee client) as application.
void	setEncoding(CharSequence encoding) Encoding for textual input and output.
void	setHost(CharSequence host) Set the server's or host's name (and address).
void	setPort(int port) The server's (the host's) port.
void	setTimeOut(int timeOut) Maximum wait time for the server's (host's) responses.
String	toString() The (main static) connection's settings as String.
String	use(String send) Use the connection — text.
String	usePingPong(String send, int maxLen) Use the connection once or for the last time — text.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

host

protected String host

The server's (the host's) name.

Name of a computer reachable via TCP/IP.

default: null

port

protected int port

The server's (the host's) port.

See Also:

getPort()

timeOut

protected int timeOut

Maximum wait time for the server's (host's) responses.

See Also:

getTimeOut(), setTimeOut(int)

encoding

protected String encoding

Encoding for textual input and output.

See Also:

getEncoding(), setEncoding(java.lang.CharSequence)

noOfAccIncMess

public volatile int noOfAccIncMess

The number of messages (still) to be accepted from server.
Provided for application use.
Intended use: count down on incoming messages and stop when 0.
default: 1 (and set so on connect() if smaller

inetAddress

protected InetAddress inetAddress

The host address.

Is set whith finally on construction.
default: null

sock

public volatile Socket sock

The socket.

The actual made connection's socket will be recorded here. Without connection or after disconnect the value is null.

Hint: sock will be provided for applications beyond the requirements of this class' methods. For performance sake the access is public. Application shall not change or this variable or store its value elsewhere.

sockIn

public volatile InputStream sockIn

The socket input stream.

The socket's actual connection input is stored here.
Value without connection or after disconnect: null.

Hint: sockIn will be provided for applications beyond the requirements of this class' methods. For performance sake the access is public. Application shall not change or this variable or store its value elsewhere.

sockOut

public volatile OutputStream sockOut

The socket output stream.

The socket's actual connection output is stored here.
Value without connection or after disconnect: null.

Hint: sockOut will be provided for applications beyond the requirements of this class' methods. For performance sake the access is public. Application shall not change or this variable or store its value elsewhere.

sockReader

public volatile BufferedReader sockReader

The socket input as Reader.

Will be made only on demand.

sockWriter

public volatile PrintWriter sockWriter

The socket output as Writer.

Will be made only on demand.

Constructor Detail

ClientLil

public ClientLil()

Method Detail

getHost

public final String getHost()

The server's (the host's) name.

Name of a computer reachable via TCP/IP.

default: null

setHost

public final void setHost(CharSequence host)
                   throws UnknownHostException

Set the server's or host's name (and address).

The name of a computer reachable via TCP/IP will be set for this Client. It will be stripped from leading and trailing white spaces before use. Null or (then) empty will default to localhost.
This setting will only be effective with the next connecting.

Parameters:

host - the server

Throws:

UnknownHostException - problems when resolving the server

getPort

public final int getPort()

The server's (the host's) port.

The server port's number (>0) to connect to.

default: 7 (echo)

setPort

public final void setPort(int port)

The server's (the host's) port.

The server port's number (>0) to connect to.

This setting will only be effective with the next connecting.

Parameters:

port - 0..65535 new port number; other values act as 7 (default)

getTimeOut

public final int getTimeOut()

Maximum wait time for the server's (host's) responses.

A value > 0 is the maximum waiting time in seconds.
A value = 0 means unlimited waiting.
A value < 0 is taken a 30s (default).
Is set by setTimeOut(int).

default: 30

setTimeOut

public final void setTimeOut(int timeOut)

Maximum wait time for the server's (host's) responses.

This setting will only be effective with the next connecting.

Parameters:

timeOut - >= 0 : the new time out value in ms; < 0 : defaults to 30s

See Also:

getTimeOut()

getEncoding

public final String getEncoding()

Encoding for textual input and output.

Is set by setEncoding(java.lang.CharSequence).

default: null (means installation's default encoding).

setEncoding

public final void setEncoding(CharSequence encoding)

Encoding for textual input and output.

This setting will only be effective with the next connecting. Allowed values are iso8859-1 (..19), utf-8 etc., see Java documentation.

Parameters:

encoding - will be stripped from enclosing white space; null or empty will default to null.

See Also:

getEncoding()

getHostAddress

public final String getHostAddress()

The host address (as String).

Returns:

null if not available

connect

public Socket connect(boolean textIO)
               throws IOException

Connecting.

A socket connection to the server's port is made. The streams and optionally the reader will be provided.

An exception occurring during the proceeding will be forwarded. A partly built up connection will be destroyed (by disconnect() in this case.

Parameters:

textIO - true: make also the Reader sockReader and Writer sockWriter

Throws:

IOException - if the connecting to host.port fails

use

public String use(String send)
           throws IOException

Use the connection — text.

If not yet done a socket connection to port is made by connect(true).

The text send if not null will be written with a closing line feed (println()) to the server. The response line will then be waited for (readln()).

An exception occurring during the proceeding will be forwarded. A partly built up connection will be destroyed (by disconnect() in this case.

Parameters:

send - text to be send to the server

Throws:

IOException - if the connecting to host:port fails

usePingPong

public String usePingPong(String send,
                          int maxLen)
                   throws IOException

Use the connection once or for the last time — text.

If a connection was (directly or indirectly via use(String)) made by connect(true) already, this method delegates to use(send) and disconnect().

Otherwise the text send will by send (as default encoded byte[] buffer) and a text of maxLen bytes received. If maxLen is outside the range 192 .. 30000 it is taken as 4090.

The connection will be closed. Exceptions on writing or reading will be forwarded; Exceptions on closing will be suppressed.

This method is thought for the (practically frequent) "Send Receive Throwaway" connections (à la ping-pong or Echo).

For a simple ping-pong connection use: usePingPong(send, 192);

Parameters:

send - text to be send to the server

maxLen - maximum length in bytes of the answer (192 .. 30000; default: 4090)

Throws:

IOException - on problems with the socket connettion to host.port

See Also:

use(String)

disconnect

public void disconnect()
                throws IOException

Disconnecting.

The socket connection made by connect() will be closed.

Hint: Another thread blocked on this connection's I/O will get a SocketException.

Throws:

IOException - on closing problems

toString

public String toString()

The (main static) connection's settings as String.

Overrides:

toString in class Object

main

public static void main(String[] args)

The ClientLil (wee client) as application.

Execute:
java de.frame4j.net.ClientLil host ["message for host"]

Example (Echo):
java de.frame4j.net.ClientLil pd310s -p 7 "try the echo"

Example (Time, Daytime, RFC 867):
java de.frame4j.net.ClientLil pd310s -p 13

Example (Quote of the day):
java de.frame4j.net.ClientLil pd310s -p 17

Example (Telnet grudge line mode only):
java de.frame4j.net.ClientLil -telnet weAut_01_a

Use
java de.frame4j.net.ClientLil [-en] -?
for help

Parameters:

args - use "-?" if in doubt