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Re: Problem with netcat
From: |
Detlev Zundel |
Subject: |
Re: Problem with netcat |
Date: |
Thu, 07 Apr 2011 18:04:49 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.0.50 (gnu/linux) |
Hi John,
> Attached is the output of two strace runs.
> strace.netcat is of 'strace -r guile --listen=9000' with 'netcat localhost
> 9000 < a.ss' run against it.
> strace.interactive is of 'strace -r guile --listen=9000' with 'netcat
> localhost 9000' used to access it and me manually typing (+ 5 3) then
> hitting <ctrl>-d in both windows to terminate.
>
> Thanks Andy and Detlev.
Thanks for the input - I think the problem is clear to see here:
> 0.000033 rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0
> 0.000039 write(90, "scheme@(guile-user)> ", 21scheme@(guile-user)> ) = 21
> 0.000028 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
> 0.000022 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0
> 0.000032 read(0, <unfinished ...>
> 30.150227 +++ killed by SIGPIPE +++
This is from the problematic log. It turns out that an "strace -f"
would have be better advice for you so we would have seen the actual
socket process but funnily enough I now sometimes can regenerate the
error (usually by pressing C-c in netcat).
This is the last I see for such a case:
[pid 706] times({tms_utime=26, tms_stime=3, tms_cutime=0, tms_cstime=0}) =
-1349846525
[pid 706] select(1024, [81], [], [], {0, 0}) = 0 (Timeout)
[pid 706] brk(0x9353000) = 0x9353000
[pid 706] brk(0x934b000) = 0x934b000
[pid 706] write(81, "scheme@(guile-user) [1]> ", 25) = 25
[pid 706] read(81, "", 1) = 0
[pid 706] write(81, "\n", 1) = 1
[pid 706] select(1024, [81], [], [], {0, 0}) = 1 (in [81], left {0, 0})
[pid 706] read(81, "", 1) = 0
[pid 706] select(1024, [81], [], [], {0, 0}) = 1 (in [81], left {0, 0})
[pid 706] read(81, "", 1) = 0
[pid 706] write(81, "\n", 1) = -1 EPIPE (Broken pipe)
[pid 706] --- SIGPIPE (Broken pipe) @ 0 (0) ---
Process 706 detached
[pid 32521] +++ killed by SIGPIPE +++
[pid 32520] +++ killed by SIGPIPE +++
+++ killed by SIGPIPE +++
So it seems like guile wants simply to output a newline but the socket
is closed already and the process then gets the SIGPIPE signal which
guile is not prepared for.
I will need to dig deeper into the innards of guile to find an answer on
how to prevent that. If someone beats me to it I'll still be happy ;)
Cheers
Detlev
--
Number theorists do it perfectly and rationally.