Re: how to get any available port
[EMAIL PROTECTED] wrote:
Apparently, calling bind() with a zero port will choose some available port
number, as demonstrated by this program:
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((, 0))
print s.getsockname()
Here's how it behaved over several runs:
$ python soc.py
('0.0.0.0', 34205)
$ python soc.py
('0.0.0.0', 34206)
$ python soc.py
('0.0.0.0', 34207)
I don't know for sure whether this is standard behavior for sockets, or
whether
it's a special behavior of linux.
It's been standard behaviour ever since the Berkeley socket interface
was defined, as far as I know.
regards
Steve
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how to get any available port
hi; if am using s.bind for a tcp socket. On the client side i dont really care which socket i use as long as i get an available socket. Is there a funciton or a way to get an available socket? thanks smadi -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Mohammed Smadi wrote: if am using s.bind for a tcp socket. On the client side i dont really care which socket i use as long as i get an available socket. Is there a funciton or a way to get an available socket? why are you using bind if you're on the client side? /F -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Hmm...perhaps he is trying to do a transfer thing like many chat programs do. Instead of sending large files across a server, you Direct Connect and send the file directly. :shrugs: -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
On 2005-10-04, ncf [EMAIL PROTECTED] wrote: Hmm...perhaps he is trying to do a transfer thing like many chat programs do. Instead of sending large files across a server, you Direct Connect and send the file directly. :shrugs: So how does that require binding the client end of a TCP connection? -- Grant Edwards grante Yow! I want you to at MEMORIZE the collected visi.compoems of EDNA ST VINCENT MILLAY... BACKWARDS!! -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Grant Edwards [EMAIL PROTECTED] writes: Hmm...perhaps he is trying to do a transfer thing like many chat programs do. Instead of sending large files across a server, you Direct Connect and send the file directly. :shrugs: So how does that require binding the client end of a TCP connection? In the nomenclature of some of these applications, that kind of transfer is called a client to client connection. Both ends are called clients. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
On 2005-10-04, Paul Rubin wrote: Grant Edwards [EMAIL PROTECTED] writes: Hmm...perhaps he is trying to do a transfer thing like many chat programs do. Instead of sending large files across a server, you Direct Connect and send the file directly. :shrugs: So how does that require binding the client end of a TCP connection? In the nomenclature of some of these applications, that kind of transfer is called a client to client connection. Both ends are called clients. IIRC, we were talking about TCP sockets. In a TCP connection, one end is the client (the one that originates the connection), and the other end is the server (the one that waits for the connection on a well-known port). The server calls bind()/listen(), and typically the client just calls connect(). In theory, the client end can call bind() to control the originating port used for the connection. But, servers don't care what the orignating port is, so on the client end bind() is usually skipped since the default connect() operation will just choose an available port. -- Grant Edwards grante Yow! It's strange, but I'm at only TRULY ALIVE when I'm visi.comcovered in POLKA DOTS and TACO SAUCE... -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Apparently, calling bind() with a zero port will choose some available port
number, as demonstrated by this program:
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((, 0))
print s.getsockname()
Here's how it behaved over several runs:
$ python soc.py
('0.0.0.0', 34205)
$ python soc.py
('0.0.0.0', 34206)
$ python soc.py
('0.0.0.0', 34207)
I don't know for sure whether this is standard behavior for sockets, or whether
it's a special behavior of linux.
Jeff
pgpdXrF07MIY9.pgp
Description: PGP signature
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Re: how to get any available port
On Tue, 4 Oct 2005, Grant Edwards wrote:
On 2005-10-04, ncf [EMAIL PROTECTED] wrote:
Hmm...perhaps he is trying to do a transfer thing like many chat
programs do. Instead of sending large files across a server, you
Direct Connect and send the file directly. :shrugs:
So how does that require binding the client end of a TCP
connection?
what else would you do? I am using examples from the web and they all
bind to a port at the localhost before connecting to the remote host.
my code is like this
#transmission socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((,hp_port)) # do some error checking
data=HI
print data
s.connect(('192.168.2.13',port))
s.send(data)
print \n
which is working fine for me after putting the
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) statement
any suggestions for alternative implementation?
moe smadi
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Re: how to get any available port
Grant Edwards [EMAIL PROTECTED] writes: In the nomenclature of some of these applications, that kind of transfer is called a client to client connection. Both ends are called clients. IIRC, we were talking about TCP sockets. Yes, but if the person was talking about using TCPs sockets in a chat application, they may have been using chat terminology rather than TCP terminology. In a typical chat app, a zillion clients all talk through TCP to a central server, which is like a phone switch. That lets Alice connect to the server and immediately see if Bob is online and what Bob's (possibly dynamic) IP address is. If Alice wants to send Bob a file, she opens a TCP connection directly to Bob. That's called a client to client connection because Alice and Bob are both clients. So, there's a reasonable application for wanting to open a listener port without binding any specific port number. Alice would just ask her OS to assign her a port (say it assigns 23789) and listen on it, instead of having to contend with other apps on the same IP for some specific port number. Then she'd send a message through the chat server asking Bob to connect to port 23789 on her machine. I'm not sure if there's a way to do this. Do you happen to know? -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
On Tue, Oct 04, 2005 at 05:19:37PM -0400, Mohammed Smadi wrote: what else would you do? I am using examples from the web and they all bind to a port at the localhost before connecting to the remote host. [...] the web must be stupider than I thought. Here's how Python's own ftplib connects to an ftp server (dedented for clarity): try: self.sock = socket.socket(af, socktype, proto) self.sock.connect(sa) except socket.error, msg: ... there's no need to call bind() before connect. Jeff pgpHhphJklBxU.pgp Description: PGP signature -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Mohammed Smadi [EMAIL PROTECTED] writes: #transmission socket s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) s.bind((,hp_port)) # do some error checking ... any suggestions for alternative implementation? In this particular instance, don't bind the transmission socket. I'm also not sure why you set SO_REUSEADDR. I've done some socket programming but am no expert. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Mohammed Smadi wrote:
what else would you do? I am using examples from the web and they all
bind to a port at the localhost before connecting to the remote host.
pointers, please.
my code is like this
#transmission socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((,hp_port)) # do some error checking
that's a typical server setup.
data=HI
print data
s.connect(('192.168.2.13',port))
s.send(data)
and this is typical client setup.
are you sure you're not cutting and pasting code from different examples?
any suggestions for alternative implementation?
if you're writing a client, get rid of the setsockopt and bind stuff.
/F
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Re: how to get any available port
On 2005-10-04, Mohammed Smadi [EMAIL PROTECTED] wrote:
On Tue, 4 Oct 2005, Grant Edwards wrote:
On 2005-10-04, ncf [EMAIL PROTECTED] wrote:
Hmm...perhaps he is trying to do a transfer thing like many chat
programs do. Instead of sending large files across a server, you
Direct Connect and send the file directly. :shrugs:
So how does that require binding the client end of a TCP
connection?
what else would you do?
Just call connect():
I am using examples from the web and they all bind to a port
at the localhost before connecting to the remote host.
I don't know who wrote those examles, but I've never seen it
done that way before. Take a look at the examples from the
python socket module docs:
http://docs.python.org/lib/socket-example.html
my code is like this
#transmission socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((,hp_port)) # do some error checking
data=HI
print data
s.connect(('192.168.2.13',port))
s.send(data)
print \n
which is working fine for me after putting the
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) statement
Just skip the bind() call. It's useless.
#transmission socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('192.168.2.13',port))
s.send(data)
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Re: how to get any available port
On 2005-10-04, Paul Rubin wrote: Mohammed Smadi [EMAIL PROTECTED] writes: #transmission socket s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) s.bind((,hp_port)) # do some error checking ... any suggestions for alternative implementation? In this particular instance, don't bind the transmission socket. I'm also not sure why you set SO_REUSEADDR. I've done some socket programming but am no expert. You set SO_REUSEADDR when you need to bind to a specific port, and you want to be able to re-use that port address for a new connection without waiting for the time specified in the TCP RFC after the old connection was closed. In the OP's case, there is no need to bind to a specific port, so just getting rid of the bind() and setsockopt() calls is the obvious answer. -- Grant Edwards grante Yow! If I had a Q-TIP, I at could prevent th' collapse visi.comof NEGOTIATIONS!! -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
On 2005-10-04, Paul Rubin wrote: Grant Edwards [EMAIL PROTECTED] writes: In the nomenclature of some of these applications, that kind of transfer is called a client to client connection. Both ends are called clients. IIRC, we were talking about TCP sockets. So, there's a reasonable application for wanting to open a listener port without binding any specific port number. Alice would just ask her OS to assign her a port (say it assigns 23789) and listen on it, instead of having to contend with other apps on the same IP for some specific port number. Then she'd send a message through the chat server asking Bob to connect to port 23789 on her machine. Ah. Got it. I'm not sure if there's a way to do this. Do you happen to know? IIRC, you just call bind() with a port number of zero, and then use some method-or-other on the bound socket to find out what port it's bound to. -- Grant Edwards grante Yow! Life is a POPULARITY at CONTEST! I'm REFRESHINGLY visi.comCANDID!! -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Grant Edwards wrote: IIRC, you just call bind() with a port number of zero, and then use some method-or-other on the bound socket to find out what port it's bound to. s = socket.socket() s.bind((, 0)) s.getsockaddr() (0.0.0.0, 4711) /F -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
Fredrik Lundh [EMAIL PROTECTED] writes: Grant Edwards wrote: IIRC, you just call bind() with a port number of zero, and then use some method-or-other on the bound socket to find out what port it's bound to. s = socket.socket() s.bind((, 0)) s.getsockaddr() (0.0.0.0, 4711) Nice. Thanks. -- http://mail.python.org/mailman/listinfo/python-list
Re: how to get any available port
In article [EMAIL PROTECTED],
[EMAIL PROTECTED] wrote:
.
.
.
Here's how it behaved over several runs:
$ python soc.py
('0.0.0.0', 34205)
$ python soc.py
('0.0.0.0', 34206)
$ python soc.py
('0.0.0.0', 34207)
I don't know for sure whether this is standard behavior for sockets, or whether
it's a special behavior of linux.
.
.
.
It is standard behavior for sockets. To my surprise, I haven't
(yet) found an RFC that specifies it, but the behavior has a deep
and wide history--even Microsoft sockets respect the convention.
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