Forum: Ruby How to realize that a TCPSocket doesn't give any more lines as answer?

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Karl W. (Guest)
on 2009-01-08 21:15
(Received via mailing list)
Hi,
I'm writing a little tcp-client which connects to a tcp-server, sends a
command and recieves an answer. If I do something like that:

#!/usr/bin/env ruby

$VERBOSE=true

require 'socket'
...
begin
  socket = TCPSocket.new($ip,$port)
rescue
  puts "error: #{$!}"
  exit 1
end

socket.print command

answer=socket.gets

socket.close


It works if the server sends just one line. But I don't know how many
lines the server answers. So I tried something like that:

answers=[]
while answer=socket.gets
  answers<<answer
end

But this results in the while-loop never ending. Even if just one line
is the answer the while loop does simply never end :( Any idea how to do
this?
Joel VanderWerf (Guest)
on 2009-01-08 23:51
(Received via mailing list)
removed_email_address@domain.invalid wrote:
>   socket = TCPSocket.new($ip,$port)
>
>
> It works if the server sends just one line. But I don't know how many lines the server 
answers. So I tried something like that:
>
> answers=[]
> while answer=socket.gets
>   answers<<answer
> end
>
> But this results in the while-loop never ending. Even if just one line is the answer the 
while loop does simply never end :( Any idea how to do this?

Try socket.gets(nil) -- that waits for EOF instead of newline.
Robert K. (Guest)
on 2009-01-09 16:22
(Received via mailing list)
2009/1/8  <removed_email_address@domain.invalid>:
>        socket = TCPSocket.new($ip,$port)
>
>
> It works if the server sends just one line. But I don't know how many lines the server 
answers. So I tried something like that:
>
> answers=[]
> while answer=socket.gets
>        answers<<answer
> end
>
> But this results in the while-loop never ending. Even if just one line is the answer the 
while loop does simply never end :( Any idea how to do this?

Basically you need to define a protocol of your own which handles
this. There are many ways to do that.  One option is to define that
there will be only one line ever.  Another option is to include
something in each like which indicates whether there is more to
follow.  Yet another option is to define a terminator sequence and use
gets or IO#each with terminator argument similar to this:

RKlemme@padrklemme1 ~
$ cat <<EOF | ruby -e 'ARGF.each("EOM") {|msg| p msg}'
> foo
> bar
> baz
> EOM
> dada
> dodo
> xxx
> EOM
> EOF
"foo\nbar\nbaz\nEOM"
"\ndada\ndodo\nxxx\nEOM"
"\n"

RKlemme@padrklemme1 ~
$

Here "EOM" is the message terminator.

Or you can use DRb if all processes are Ruby processes.  Then it's
handled by DRb and you just invoke methods.

Kind regards

robert
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