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Groups > comp.lang.python > #61715
| From | Grant Edwards <invalid@invalid.invalid> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: [newbie] trying socket as a replacement for nc |
| Date | 2013-12-12 14:16 +0000 |
| Organization | PANIX Public Access Internet and UNIX, NYC |
| Message-ID | <l8cggd$fl9$1@reader1.panix.com> (permalink) |
| References | <efae1b3c-c9c5-4ef4-8e94-7fbe8716ab53@googlegroups.com> <mailman.3939.1386804043.18130.python-list@python.org> |
On 2013-12-11, Dan Stromberg <drsalists@gmail.com> wrote:
> On Wed, Dec 11, 2013 at 3:08 PM, Jean Dubois <jeandubois314@gmail.com>wrote:
>
>> I have an ethernet-rs232 adapter which allows me to connect to a
>> measurement instrument by means of netcat on a linux system.
>> e.g. entering nc 10.128.59.63 7000
>> allows me to enter e.g.
>> *IDN?
>> after which I get an identification string of the measurement instrument
>> back.
>> I thought I could accomplish the same using the python module "socket"
>> and tried out the sample program below which doesn't work however:
>>
>
> Sockets reserve the right to split one socket.send() into multiple
> socket.recv()'s on the other end of the communication, or to aggregate
> multiple socket.send()'s into a single socket.recv() - pretty much any way
> the relevant IP stacks and communications equipment feel like for the sake
> of performance or reliability.
Just to be pedantic: _TCP_ sockets reserver that right. UDP sockets
do not, and do in fact guarantee that each message is discrete. [It
appears that the OP is undoubtedly using TCP sockets.]
> The confusing thing about this is, it won't be done on every
> transmission - in fact, it'll probably happen rather seldom unless
> you're on a heavy loaded network or have some MTU issues (see Path
> MTU Discovery, and bear in mind that paths can change during a TCP
> session). But writing your code assuming it will never happen is a
> bad idea.
And it _will_ fail someday in some odd circumstance when, for example,
some customer is be using it via a dial-up PPP connection, or there is
a satellite link in the path, or there's a flakey router somewhere,
or...
--
Grant Edwards grant.b.edwards Yow! Those people look
at exactly like Donnie and
gmail.com Marie Osmond!!
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[newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-11 15:08 -0800
Re: [newbie] trying socket as a replacement for nc Dan Stromberg <drsalists@gmail.com> - 2013-12-11 15:20 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-12 00:28 -0800
Re: [newbie] trying socket as a replacement for nc Dan Stromberg <drsalists@gmail.com> - 2013-12-12 13:23 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-12 19:23 -0800
Re: [newbie] trying socket as a replacement for nc Dan Stromberg <drsalists@gmail.com> - 2013-12-12 19:32 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-13 03:03 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-13 03:56 -0800
Re: [newbie] trying socket as a replacement for nc Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-13 08:35 +0000
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-13 04:20 -0800
Re: [newbie] trying socket as a replacement for nc rusi <rustompmody@gmail.com> - 2013-12-13 09:04 -0800
Re: [newbie] trying socket as a replacement for nc rusi <rustompmody@gmail.com> - 2013-12-13 09:09 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-14 05:11 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-14 05:14 -0800
Re: [newbie] trying socket as a replacement for nc Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-14 13:29 +0000
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-16 01:40 -0800
Re: [newbie] trying socket as a replacement for nc Ervin Hegedüs <airween@gmail.com> - 2013-12-16 11:04 +0100
Re: [newbie] trying socket as a replacement for nc Grant Edwards <invalid@invalid.invalid> - 2013-12-12 14:16 +0000
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-13 01:23 +1100
Re: [newbie] trying socket as a replacement for nc Dan Stromberg <drsalists@gmail.com> - 2013-12-12 13:27 -0800
Re: [newbie] trying socket as a replacement for nc Grant Edwards <invalid@invalid.invalid> - 2013-12-13 16:06 +0000
Re: [newbie] trying socket as a replacement for nc Dan Stromberg <drsalists@gmail.com> - 2013-12-14 17:24 -0800
Re: [newbie] trying socket as a replacement for nc Grant Edwards <invalid@invalid.invalid> - 2013-12-15 15:15 +0000
Re: [newbie] trying socket as a replacement for nc Roy Smith <roy@panix.com> - 2013-12-15 10:51 -0500
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-16 03:04 +1100
Re: [newbie] trying socket as a replacement for nc Roy Smith <roy@panix.com> - 2013-12-15 12:44 -0500
Re: [newbie] trying socket as a replacement for nc Grant Edwards <invalid@invalid.invalid> - 2013-12-15 22:42 +0000
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-16 09:48 +1100
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-13 08:58 +1100
Re: [newbie] trying socket as a replacement for nc Grant Edwards <invalid@invalid.invalid> - 2013-12-13 16:10 +0000
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-14 03:19 +1100
Re: [newbie] trying socket as a replacement for nc Grant Edwards <invalid@invalid.invalid> - 2013-12-13 16:57 +0000
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-14 04:05 +1100
Re: [newbie] trying socket as a replacement for nc 88888 Dihedral <dihedral88888@gmail.com> - 2013-12-16 04:38 -0800
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-16 23:59 +1100
Re: [newbie] trying socket as a replacement for nc Roy Smith <roy@panix.com> - 2013-12-16 09:03 -0500
Re: [newbie] trying socket as a replacement for nc 88888 Dihedral <dihedral88888@gmail.com> - 2013-12-18 23:20 -0800
Re: [newbie] trying socket as a replacement for nc Dave Angel <davea@davea.name> - 2013-12-12 19:52 -0500
Re: [newbie] trying socket as a replacement for nc Conor Hughes <conorh@conorh.net> - 2013-12-11 15:38 -0800
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-12 00:08 -0800
Re: [newbie] trying socket as a replacement for nc Chris Angelico <rosuav@gmail.com> - 2013-12-12 19:21 +1100
Re: [newbie] trying socket as a replacement for nc Jean Dubois <jeandubois314@gmail.com> - 2013-12-12 01:21 -0800
Re: [newbie] trying socket as a replacement for nc Alister <alister.ware@ntlworld.com> - 2013-12-12 14:05 +0000
Re: [newbie] trying socket as a replacement for nc Alister <alister.ware@ntlworld.com> - 2013-12-12 14:05 +0000
Re: [newbie] trying socket as a replacement for nc Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-12-12 14:34 +0000
Re: [newbie] trying socket as a replacement for nc Christian Gollwitzer <auriocus@gmx.de> - 2013-12-13 00:43 +0100
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