Java sockets: Program stops at socket.getInputStream() w/o error?

Question

InetAddress host = InetAddress.getLocalHost();
Socket link = new Socket(host, Integer.parseInt(args[0]));
System.out.println("before input stream");
ObjectInputStream in = new ObjectInputStream(link.getInputStream());
System.out.println("before output stream");
ObjectInputStream out = new ObjectOutputStream(link.getOutputStream());

"before input stream" is the last lifesign on cmd-line. There is no Exception thrown. Why is this happening? I don't understand...

args[0] is 5000. //edit: flush doesn't help.

have you run it from the debugger? perhaps that'll break into the code and give you an idea of whats going on. — Nerdtron
– Nerdtron, Commented Nov 18, 2011 at 17:14
@user Last line in your code doesn't compile. ..Input.. out = new ..Output.. — Vlad
– Vlad, Commented Nov 18, 2011 at 17:17
Also: ObjectInputStream out = new ObjectOutputStream(link.getOutputStream()); — Tudor
– Tudor, Commented Nov 18, 2011 at 17:17

thomas · Accepted Answer · 2011-11-18 17:16:39Z

22

This is because the ObjectInputStream(InputStream in)-constructor is a blocking-call if the inputStream is empty.

Quote:

Creates an ObjectInputStream that reads from the specified InputStream. A serialization stream header is read from the stream and verified. This constructor will block until the corresponding ObjectOutputStream has written and flushed the header.

answered Nov 18, 2011 at 17:16

thomas

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3 Comments

user1054247 Over a year ago

so if i make the outputstream on the client and on the server side first, that should work? interessting.... i will give it a try. thanks.

user1054247 Over a year ago

well yes. if I exchange the creation of the streams it works. like written below, the ObjectInputStream out-thing is just a typo. thanks@all!

LAMRIN TAWSRAS Over a year ago

Very basic thing but very necessary to know. Thanks man you saved my days

Matt · Accepted Answer · 2011-11-18 17:19:50Z

0

Possibly,

link.getInputStream();

could be returning null, though that should return an error by looking at the class files. Another thing I noticed was, you declare:

ObjectInputStream out = new ObjectOutputStream(link.getOutputStream());

From this, you are stating a ObjectInputStream as a ObjectOutputStream without a cast (Would not be appropriate here anyways)

you should try:

ObjectOutputStream out = new ObjectOutputStream(link.getOutputStream());

This should work, as the script may queue the System.out, but notice the error before it can be initialized.

Tell me if this works :D

answered Nov 18, 2011 at 17:19

Matt

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