范例
¶
Here are four minimal example programs using the TCP/IP protocol: a server that echoes all data that it receives back (servicing only one client), and a client using it. Note that a server must perform the sequence
socket()
,
bind()
,
listen()
,
accept()
(possibly repeating the
accept()
to service more than one client), while a client only needs the sequence
socket()
,
connect()
. Also note that the server does not
sendall()
/
recv()
on the socket it is listening on but on the new socket returned by
accept()
.
前 2 范例仅支持 IPv4。
# Echo server program
import socket
HOST = '' # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
with conn:
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
# Echo client program
import socket
HOST = 'daring.cwi.nl' # The remote host
PORT = 50007 # The same port as used by the server
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.connect((HOST, PORT))
s.sendall(b'Hello, world')
data = s.recv(1024)
print('Received', repr(data))
The next two examples are identical to the above two, but support both IPv4 and IPv6. The server side will listen to the first address family available (it should listen to both instead). On most of IPv6-ready systems, IPv6 will take precedence and the server may not accept IPv4 traffic. The client side will try to connect to all the addresses returned as a result of the name resolution, and sends traffic to the first one connected successfully.
# Echo server program
import socket
import sys
HOST = None # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC,
socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
af, socktype, proto, canonname, sa = res
try:
s = socket.socket(af, socktype, proto)
except OSError as msg:
s = None
continue
try:
s.bind(sa)
s.listen(1)
except OSError as msg:
s.close()
s = None
continue
break
if s is None:
print('could not open socket')
sys.exit(1)
conn, addr = s.accept()
with conn:
print('Connected by', addr)
while True:
data = conn.recv(1024)
if not data: break
conn.send(data)
# Echo client program
import socket
import sys
HOST = 'daring.cwi.nl' # The remote host
PORT = 50007 # The same port as used by the server
s = None
for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM):
af, socktype, proto, canonname, sa = res
try:
s = socket.socket(af, socktype, proto)
except OSError as msg:
s = None
continue
try:
s.connect(sa)
except OSError as msg:
s.close()
s = None
continue
break
if s is None:
print('could not open socket')
sys.exit(1)
with s:
s.sendall(b'Hello, world')
data = s.recv(1024)
print('Received', repr(data))
The next example shows how to write a very simple network sniffer with raw sockets on Windows. The example requires administrator privileges to modify the interface:
import socket
# the public network interface
HOST = socket.gethostbyname(socket.gethostname())
# create a raw socket and bind it to the public interface
s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IP)
s.bind((HOST, 0))
# Include IP headers
s.setsockopt(socket.IPPROTO_IP, socket.IP_HDRINCL, 1)
# receive all packets
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_ON)
# receive a packet
print(s.recvfrom(65565))
# disabled promiscuous mode
s.ioctl(socket.SIO_RCVALL, socket.RCVALL_OFF)
The next example shows how to use the socket interface to communicate to a CAN network using the raw socket protocol. To use CAN with the broadcast manager protocol instead, open a socket with:
socket.socket(socket.AF_CAN, socket.SOCK_DGRAM, socket.CAN_BCM)
After binding (
CAN_RAW
) or connecting (
CAN_BCM
) the socket, you can use the
socket.send()
and
socket.recv()
operations (and their counterparts) on the socket object as usual.
此最后范例可能要求特殊权限：
import socket
import struct
# CAN frame packing/unpacking (see 'struct can_frame' in <linux/can.h>)
can_frame_fmt = "=IB3x8s"
can_frame_size = struct.calcsize(can_frame_fmt)
def build_can_frame(can_id, data):
can_dlc = len(data)
data = data.ljust(8, b'\x00')
return struct.pack(can_frame_fmt, can_id, can_dlc, data)
def dissect_can_frame(frame):
can_id, can_dlc, data = struct.unpack(can_frame_fmt, frame)
return (can_id, can_dlc, data[:can_dlc])
# create a raw socket and bind it to the 'vcan0' interface
s = socket.socket(socket.AF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
s.bind(('vcan0',))
while True:
cf, addr = s.recvfrom(can_frame_size)
print('Received: can_id=%x, can_dlc=%x, data=%s' % dissect_can_frame(cf))
try:
s.send(cf)
except OSError:
print('Error sending CAN frame')
try:
s.send(build_can_frame(0x01, b'\x01\x02\x03'))
except OSError:
print('Error sending CAN frame')
Running an example several times with too small delay between executions, could lead to this error:
OSError: [Errno 98] Address already in use
This is because the previous execution has left the socket in a
TIME_WAIT
state, and can’t be immediately reused.
有
socket
标志要设置，为阻止此
socket.SO_REUSEADDR
:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((HOST, PORT))
the
SO_REUSEADDR
flag tells the kernel to reuse a local socket in
TIME_WAIT
state, without waiting for its natural timeout to expire.
另请参阅
有关套接字编程 (在 C 中) 的介绍，见以下论文：
-
An Introductory 4.3BSD Interprocess Communication Tutorial
, by Stuart Sechrest
-
An Advanced 4.3BSD Interprocess Communication Tutorial
, by Samuel J. Leffler et al,
both in the UNIX Programmer’s Manual, Supplementary Documents 1 (sections PS1:7 and PS1:8). The platform-specific reference material for the various socket-related system calls are also a valuable source of information on the details of socket semantics. For Unix, refer to the manual pages; for Windows, see the WinSock (or Winsock 2) specification. For IPv6-ready APIs, readers may want to refer to
RFC 3493
titled Basic Socket Interface Extensions for IPv6.
