Blocking hasNextLine() method

[Ash maker]

Hello,
I use a scanner to read data from a socket. I do not know how many rows the server will send me back, I am thus:

while(monScanner.hasNextLine())
{
     String tm = monScanner.nextLine();
     / / Processing
}

However, this loop blocks the hasNextLine () last name, which must return false. I do not know why. How to prevent it from blocking?

Thank you

Fred

[InterNetWorKed]

Hello,
If the remote machine has not closed the socket is completely normal. Scanner uses a buffer that reads data from the source, and finds himself blocked by the read ().
So two solutions:
- Either the remote machine will no longer use the socket and it should close.
- Either it must still use it, and there you are obliged to observe a certain protocol to know the amount of data to read without being blocked.

[Ash maker]

Hey
In fact, the problem is that I use this reader for a small project Server / FTP client. When I make a list, I do not know when I'll stop reading, but I can not afford to close the socket under the pretext that the client will block. What do you think when you talk about protocol? Not because I see which protocol I use to tell my client "you will read 10 lines". If you any solution for this then please guide me.

[NetworkeR]

Hello,
The communication protocol between your client and your server: you are obliged to have one to communicate. it's just the rules of communication (style, I send "this", I replied "that" if it's good or "something else" if it is not good). When you talk about FTP, you mean the real FTP (ie respecting RFC) Is an application or file transfer using its own commands? Because normally with FTP when you make a LIST server simply returns a response style OK or NOT OK and data is sent over another socket, which is closed at the end.

[Ash maker]

Hello,
The goal is to make a "pseudo" customer / ftp server, it does not make a real server and ftp client, because the course we do not, it's too big to respect the RFC. So, I think I'll pass the number of files before sending the list actually. The only thing I did not understand why this function is "verification" that does that look if there is something to read can block?

[Linux-Us]

Hello,
Scanner reads theInputStream and stored in a buffer so that the parser. So when you make a hasNextLine () it reads as a buffer or in theInputStream to see if there are data. But if the server finished sending data class scanner will block because the buffer is empty and the method read () 'InputStream' will block (because there's nothing to read). Indeed, read () not return -1 as in the case where the end of stream is reached, and a socket that only occurs when closing the socket. So if you want to keep the socket open you have to use another means to prevent blocking read and move on.