Python <-> C via sockets

**Rene Pijlman** · Jul 18 '05, 02:54 AM

Re: Python <-> C via sockets

Nick Keighley:[color=blue]
>is there a known problem with getting a Python based socket program to
>communicate with a C based socket program?[/color]

No. Client and server are completely independent and can be implemented in
any language.

They must speak the same application level protocol of course, on top of
TCP/IP.

--
René Pijlman

**Eric Brunel** · Jul 18 '05, 02:54 AM

Re: Python <-> C via sockets

Nick Keighley wrote:[color=blue]
> I'm probably missing something rather obvious, but is there a known
> problem with getting a Python based socket program to communicate with
> a C based socket program? A simple echo server written in Python
> (the example from Python in a Nutshell actually) will happily talk
> to a Python based client. If a C based client is substitued the connection
> is refused (or so the C client reports). The C client will talk to
> a C server.[/color]

Communications between C and Python via sockets definetly work: we do that every
day (no kidding ;-)

Can you post an example of your code?
--
- Eric Brunel <eric dot brunel at pragmadev dot com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com

**Nick Keighley** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Eric Brunel <eric.brunel@pr agmadev.N0SP4M. com> wrote in message news:<bkroq8$8u d$1@news-reader1.wanadoo .fr>...[color=blue]
> Nick Keighley wrote:[/color]
[color=blue][color=green]
> > I'm probably missing something rather obvious, but is there a known
> > problem with getting a Python based socket program to communicate with
> > a C based socket program? A simple echo server written in Python
> > (the example from Python in a Nutshell actually) will happily talk
> > to a Python based client. If a C based client is substitued the connection
> > is refused (or so the C client reports). The C client will talk to
> > a C server.[/color]
>
> Communications between C and Python via sockets definetly work: we do that
> every day (no kidding ;-)
>
> Can you post an example of your code?[/color]

well I assumed sockets actually worked I was guessing the slight
differences in the interfaces caused me to set the two ends up
slightly
differently.

Python Echo Server
------------------
import socket

DEFAULT_PROTOCO L = 0
PORT = 8702

sock = socket.socket (socket.AF_INET , socket.SOCK_STR EAM,
DEFAULT_PROTOCO L)
sock.bind (('', PORT))
sock.listen (5)

# wait for a connection
try:
while True:
newSocket, address = sock.accept ()
print "connected from", address
while True:
receivedData = newSocket.recv (8192)
if not receivedData:
break
print "received: ", receivedData
newSocket.senda ll (receivedData)
newSocket.close ()
print "disconnect ed from", address
finally:
sock.close ()
---------------------------------------------------------------------
C echo client (includes omitted)
-------------------------------
#define DEFAULT_PROTOCO L 0
#define PORT 8702
#define HOST "localhost"
/* #define HOST "127.0.0.1" */
/* #define HOST "cmopc018" */
#define TYPE SOCK_STREAM

int main (void)
{
struct hostent *phe;
struct sockaddr_in sin;
int s;

s = socket (PF_INET, TYPE, DEFAULT_PROTOCO L);
if (s < 0)
raise_report (LEVEL_FATAL, "tiny_echo" , "can't create socket:
%s", strerror (errno));

/*
* connect to the socket
*/

memset (&sin, 0, sizeof sin);
sin.sin_family = AF_INET;
sin.sin_port = PORT;
if ((phe = gethostbyname (HOST)))
{
memcpy (&sin.sin_add r, phe->h_addr_list[0], phe->h_length);
raise_report (LEVEL_INFO, "tiny_echo" , "addr is %X",
sin.sin_addr);
}
else
if ((sin.sin_addr. s_addr = inet_addr (HOST)) == INADDR_NONE)
raise_report (LEVEL_FATAL, "tiny_echo" , "can't get \"%s\"
host entry", HOST);

if (connect (s, (struct sockaddr *)&sin, sizeof sin) < 0)
raise_report (LEVEL_FATAL, "tiny_echo" , "can't connect to
%s.%d: %s", HOST, sin.sin_port, strerror (errno));

raise_report (LEVEL_INFO, "tiny_echo" , "CONNECTED" );

return 0;
}
------------------------------------------------------------------------------

--
Nick Keighley

**Nick Keighley** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Eric Brunel <eric.brunel@pr agmadev.N0SP4M. com> wrote in message news:<bkroq8$8u d$1@news-reader1.wanadoo .fr>...[color=blue]
> Nick Keighley wrote:[/color]
[color=blue][color=green]
> > I'm probably missing something rather obvious, but is there a known
> > problem with getting a Python based socket program to communicate with
> > a C based socket program? A simple echo server written in Python
> > (the example from Python in a Nutshell actually) will happily talk
> > to a Python based client. If a C based client is substitued the connection
> > is refused (or so the C client reports). The C client will talk to
> > a C server.[/color]
>
> Communications between C and Python via sockets definetly work: we do that
> every day (no kidding ;-)
>
> Can you post an example of your code?[/color]

well I assumed sockets actually worked I was guessing the slight
differences in the interfaces caused me to set the two ends up
slightly
differently.

Python Echo Server
------------------
import socket

DEFAULT_PROTOCO L = 0
PORT = 8702

sock = socket.socket (socket.AF_INET , socket.SOCK_STR EAM,
DEFAULT_PROTOCO L)
sock.bind (('', PORT))
sock.listen (5)

# wait for a connection
try:
while True:
newSocket, address = sock.accept ()
print "connected from", address
while True:
receivedData = newSocket.recv (8192)
if not receivedData:
break
print "received: ", receivedData
newSocket.senda ll (receivedData)
newSocket.close ()
print "disconnect ed from", address
finally:
sock.close ()
---------------------------------------------------------------------
C echo client (includes omitted)
-------------------------------
#define DEFAULT_PROTOCO L 0
#define PORT 8702
#define HOST "localhost"
/* #define HOST "127.0.0.1" */
/* #define HOST "cmopc018" */
#define TYPE SOCK_STREAM

int main (void)
{
struct hostent *phe;
struct sockaddr_in sin;
int s;

s = socket (PF_INET, TYPE, DEFAULT_PROTOCO L);
if (s < 0)
raise_report (LEVEL_FATAL, "tiny_echo" , "can't create socket:
%s", strerror (errno));

/*
* connect to the socket
*/

memset (&sin, 0, sizeof sin);
sin.sin_family = AF_INET;
sin.sin_port = PORT;
if ((phe = gethostbyname (HOST)))
{
memcpy (&sin.sin_add r, phe->h_addr_list[0], phe->h_length);
raise_report (LEVEL_INFO, "tiny_echo" , "addr is %X",
sin.sin_addr);
}
else
if ((sin.sin_addr. s_addr = inet_addr (HOST)) == INADDR_NONE)
raise_report (LEVEL_FATAL, "tiny_echo" , "can't get \"%s\"
host entry", HOST);

if (connect (s, (struct sockaddr *)&sin, sizeof sin) < 0)
raise_report (LEVEL_FATAL, "tiny_echo" , "can't connect to
%s.%d: %s", HOST, sin.sin_port, strerror (errno));

raise_report (LEVEL_INFO, "tiny_echo" , "CONNECTED" );

return 0;
}
------------------------------------------------------------------------------

--
Nick Keighley

**Rene Pijlman** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Nick Keighley:[color=blue]
> sin.sin_port = PORT;[/color]

"serv_addr.sin_ port = htons(portno);

The second field of serv_addr is unsigned short sin_port , which contain
the port number. However, instead of simply copying the port number to
this field, it is necessary to convert this to network byte order using
the function htons() which converts a port number in host byte order to a
port number in network byte order."

404 Not Found

http://www.cs.rpi.edu/courses/sysprog/sockets/sock.html

--
René Pijlman

**Rene Pijlman** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Nick Keighley:[color=blue]
> sin.sin_port = PORT;[/color]

"serv_addr.sin_ port = htons(portno);

The second field of serv_addr is unsigned short sin_port , which contain
the port number. However, instead of simply copying the port number to
this field, it is necessary to convert this to network byte order using
the function htons() which converts a port number in host byte order to a
port number in network byte order."

404 Not Found

http://www.cs.rpi.edu/courses/sysprog/sockets/sock.html

--
René Pijlman

**Nick Keighley** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Eric Brunel <eric.brunel@pr agmadev.N0SP4M. com> wrote in message news:<bkroq8$8u d$1@news-reader1.wanadoo .fr>...[color=blue]
> Nick Keighley wrote:[color=green]
> > I'm probably missing something rather obvious, but is there a known
> > problem with getting a Python based socket program to communicate with
> > a C based socket program? A simple echo server written in Python
> > (the example from Python in a Nutshell actually) will happily talk
> > to a Python based client. If a C based client is substitued the connection
> > is refused (or so the C client reports). The C client will talk to
> > a C server.[/color]
>
> Communications between C and Python via sockets definetly work: we do that
> every day (no kidding ;-)
>
> Can you post an example of your code?[/color]

by the time you read this the posted code may have appeared.
A call to htons() (convert unsigned short to network byte order)
was ommitted on the C side.

this line:-
sin.sin_port = PORT;

should read:-
sin.sin_port = htons(PORT);

thanks!

--
Nick Keighley

**Nick Keighley** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Eric Brunel <eric.brunel@pr agmadev.N0SP4M. com> wrote in message news:<bkroq8$8u d$1@news-reader1.wanadoo .fr>...[color=blue]
> Nick Keighley wrote:[color=green]
> > I'm probably missing something rather obvious, but is there a known
> > problem with getting a Python based socket program to communicate with
> > a C based socket program? A simple echo server written in Python
> > (the example from Python in a Nutshell actually) will happily talk
> > to a Python based client. If a C based client is substitued the connection
> > is refused (or so the C client reports). The C client will talk to
> > a C server.[/color]
>
> Communications between C and Python via sockets definetly work: we do that
> every day (no kidding ;-)
>
> Can you post an example of your code?[/color]

by the time you read this the posted code may have appeared.
A call to htons() (convert unsigned short to network byte order)
was ommitted on the C side.

this line:-
sin.sin_port = PORT;

should read:-
sin.sin_port = htons(PORT);

thanks!

--
Nick Keighley

**Eric Brunel** · Jul 18 '05, 02:55 AM

Re: Python <-> C via sockets

Nick Keighley wrote:[color=blue]
> Eric Brunel <eric.brunel@pr agmadev.N0SP4M. com> wrote in message news:<bkroq8$8u d$1@news-reader1.wanadoo .fr>...
>[color=green]
>>Nick Keighley wrote:[/color]
>
>[color=green][color=darkred]
>>>I'm probably missing something rather obvious, but is there a known
>>>problem with getting a Python based socket program to communicate with
>>>a C based socket program? A simple echo server written in Python
>>>(the example from Python in a Nutshell actually) will happily talk
>>>to a Python based client. If a C based client is substitued the connection
>>>is refused (or so the C client reports). The C client will talk to
>>>a C server.[/color]
>>
>>Communication s between C and Python via sockets definetly work: we do that
>>every day (no kidding ;-)
>>
>>Can you post an example of your code?[/color]
>
>
> well I assumed sockets actually worked I was guessing the slight
> differences in the interfaces caused me to set the two ends up
> slightly
> differently.
>
> Python Echo Server
> ------------------
> import socket
>
> DEFAULT_PROTOCO L = 0
> PORT = 8702
>
> sock = socket.socket (socket.AF_INET , socket.SOCK_STR EAM,
> DEFAULT_PROTOCO L)
> sock.bind (('', PORT))
> sock.listen (5)
>
> # wait for a connection
> try:
> while True:
> newSocket, address = sock.accept ()
> print "connected from", address
> while True:
> receivedData = newSocket.recv (8192)
> if not receivedData:
> break
> print "received: ", receivedData
> newSocket.senda ll (receivedData)
> newSocket.close ()
> print "disconnect ed from", address
> finally:
> sock.close ()
> ---------------------------------------------------------------------
> C echo client (includes omitted)
> -------------------------------
> #define DEFAULT_PROTOCO L 0
> #define PORT 8702
> #define HOST "localhost"
> /* #define HOST "127.0.0.1" */
> /* #define HOST "cmopc018" */
> #define TYPE SOCK_STREAM
>
>
> int main (void)
> {
> struct hostent *phe;
> struct sockaddr_in sin;
> int s;
>
> s = socket (PF_INET, TYPE, DEFAULT_PROTOCO L);
> if (s < 0)
> raise_report (LEVEL_FATAL, "tiny_echo" , "can't create socket:
> %s", strerror (errno));
>
>
> /*
> * connect to the socket
> */
>
> memset (&sin, 0, sizeof sin);
> sin.sin_family = AF_INET;
> sin.sin_port = PORT;
> if ((phe = gethostbyname (HOST)))
> {
> memcpy (&sin.sin_add r, phe->h_addr_list[0], phe->h_length);
> raise_report (LEVEL_INFO, "tiny_echo" , "addr is %X",
> sin.sin_addr);
> }
> else
> if ((sin.sin_addr. s_addr = inet_addr (HOST)) == INADDR_NONE)
> raise_report (LEVEL_FATAL, "tiny_echo" , "can't get \"%s\"
> host entry", HOST);
>
> if (connect (s, (struct sockaddr *)&sin, sizeof sin) < 0)
> raise_report (LEVEL_FATAL, "tiny_echo" , "can't connect to
> %s.%d: %s", HOST, sin.sin_port, strerror (errno));
>
> raise_report (LEVEL_INFO, "tiny_echo" , "CONNECTED" );
>
> return 0;
> }
> ------------------------------------------------------------------------------[/color]

After adding the missing htons and replacing the raise_report's by printf's,
works like a charm here (Linux Mandrake 8.0 with Python 2.1).

What is exactly the error you get?
--
- Eric Brunel <eric dot brunel at pragmadev dot com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com

**Nick Keighley** · Jul 18 '05, 02:56 AM

Re: Python <-> C via sockets

Rene Pijlman <reply.in.the.n ewsgroup@my.add ress.is.invalid > wrote in message news:<6f83nv47k 9m7qm4pace4lvfd faqmof47ei@4ax. com>...
[color=blue]
> http://www.cs.rpi.edu/courses/sysprog/sockets/sock.html[/color]

looks handy!

**anuradha.k.r@sify.com** · Jul 18 '05, 02:59 AM

Re: Python <-> C via sockets

hi,
I 've already posted a message to this group but i think You guys can
provide a solution faster.My problem is similar ,my client side
(written in python) is not able to connect to the server side
(written in C) in the same machine.
my server side works perfectly fine and it waits for a connection to b
established.How ever my client gives error "10061.connecti on
refused".Will send you the code of both server side and client side.:

server side:
------------
#include<stdio. h>
#include<winsoc k2.h>
#include <windows.h>

SOCKET recvSock,WinSoc ket,slisten;
WSADATA WSAData;
SOCKADDR_IN Acceptor;
SOCKADDR_IN Connector;
int TypeOfCon;
int Initialise();
SOCKET ListenSocket();
int RecvBuff(BYTE * RecdBuffer,int size);
void Close();
unsigned char * RecdBuffer;

int main()
{
int flag;
flag = Initialise();
slisten= ListenSocket();
flag = RecvBuff(RecdBu ffer,20);
Close();
return 1;
}

int Initialise()
{
WSAStartup (MAKEWORD(1,1), &WSAData);
WinSocket = socket (AF_INET/*2*/, SOCK_STREAM/*1*/, 0);
recvSock = socket (AF_INET/*2*/, SOCK_STREAM/*1*/, 0);
return 1;
}

SOCKET ListenSocket()
{
int error;
int sizeofaddr;
sizeofaddr = sizeof(Acceptor );

/*BOOL mcast ;
mcast= TRUE;*/

Acceptor.sin_ad dr.S_un.S_addr = htonl(INADDR_AN Y);
Acceptor.sin_fa mily = AF_INET;
Acceptor.sin_po rt = 9999;

bind(WinSocket, (const SOCKADDR *)&Acceptor,siz eof(Acceptor));
error = GetLastError();
if(error)
{
return 0;
}

listen(WinSocke t,1);
error = GetLastError();
if(error)
{
return 0;
}
recvSock = accept((SOCKET) WinSocket,(SOCK ADDR
*)&Acceptor,&si zeofaddr);

error = GetLastError();
if(error)
{
return 0;
}
return recvSock;

}

int RecvBuff(BYTE * Buffer,int size)
{
int amount,error;

amount = recv(recvSock,( char *)Buffer,size,0 );
error = GetLastError();
if(error)
{
return 0;
}
else
return 1;
}

void Close()
{
closesocket(Win Socket);
closesocket(rec vSock);
}

client side:
-------------

import socket

#HOST = '130.10.5.38' # The remote host
#PORT = 50007 # The same port as used by the server
try:
s = socket.socket(s ocket.AF_INET, socket.SOCK_STR EAM)
except socket.error:
print 'socket not creadted'
try:
s.connect(("130 .10.5.38", 9999))
except socket.error,ms g:
print 'error in connect'

#s.send('Hello, world')
#data = s.recv(1024)
s.close()
#print 'Received', `data`

I'd gone thru the discussion above,so i guess probably the problem
with my code is also on the port address only.Pls help.
thanx,
AKR.

nick.keighley@m arconi.com (Nick Keighley) wrote in message news:<8ad2cfb3. 0309240628.dbbc a33@posting.goo gle.com>...[color=blue]
> Eric Brunel <eric.brunel@pr agmadev.N0SP4M. com> wrote in message news:<bkroq8$8u d$1@news-reader1.wanadoo .fr>...[color=green]
> > Nick Keighley wrote:[color=darkred]
> > > I'm probably missing something rather obvious, but is there a known
> > > problem with getting a Python based socket program to communicate with
> > > a C based socket program? A simple echo server written in Python
> > > (the example from Python in a Nutshell actually) will happily talk
> > > to a Python based client. If a C based client is substitued the connection
> > > is refused (or so the C client reports). The C client will talk to
> > > a C server.[/color]
> >
> > Communications between C and Python via sockets definetly work: we do that
> > every day (no kidding ;-)
> >
> > Can you post an example of your code?[/color]
>
> by the time you read this the posted code may have appeared.
> A call to htons() (convert unsigned short to network byte order)
> was ommitted on the C side.
>
> this line:-
> sin.sin_port = PORT;
>
> should read:-
> sin.sin_port = htons(PORT);
>
>
> thanks![/color]

Python <-> C via sockets

Python <-> C via sockets

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