[newbie] trying socket as a replacement for nc

Jean Dubois jeandubois314 at gmail.com
Thu Dec 12 09:28:32 CET 2013


On Thursday, December 12, 2013 12:20:36 AM UTC+1, Dan Stromberg wrote:
> On Wed, Dec 11, 2013 at 3:08 PM, Jean Dubois <jeandu... at 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.
> 
> 
> 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.
> 
> 
> 
> For this reason, I wrote http://stromberg.dnsalias.org/~strombrg/bufsock.html , which abstracts away these complications, and actually makes things pretty simple.  There are examples on the web page.
> 
> 
> 
> HTH

Dear Dan, 
Could you copy paste here the code for your function I have to add to my "program"?

thanks in advance
jean



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