How-to — UDP Client Endpoints
Note
This page uses two different API variants:
Synchronous API with classic
def
functions, usable in any context.Asynchronous API with
async def
functions, using an asynchronous framework to perform I/O operations.
All asynchronous API examples assume that you are using asyncio
,
but you can use a different library thanks to the asynchronous backend engine API.
The Basics
The Protocol Object
The UDP clients expect a DatagramProtocol
instance to communicate with the remote endpoint.
See also
- How-to — Communication Protocols
Explains what a
DatagramProtocol
is and how to use it.
Connecting To The Remote Host
Important
If you are familiar with UDP sockets, you know that there are no real connections (communication pipes) like there are with TCP sockets.
If not, I advise you to read the Unix manual pages udp(7) and connect(2).
You need the host address (domain name or IP) and the port of connection in order to connect to the remote host:
1from __future__ import annotations
2
3from easynetwork.api_sync.client import UDPNetworkClient
4from easynetwork.protocol import DatagramProtocol
5from easynetwork.serializers import JSONSerializer
6
7
8def main() -> None:
9 protocol = DatagramProtocol(JSONSerializer())
10 address = ("127.0.0.1", 9000)
11
12 with UDPNetworkClient(address, protocol) as client:
13 print(f"Remote address: {client.get_remote_address()}")
14
15 ...
16
17
18if __name__ == "__main__":
19 main()
Note
The client does nothing when it enters the with
context. Everything is done on object creation.
1from __future__ import annotations
2
3import asyncio
4
5from easynetwork.api_async.client import AsyncUDPNetworkClient
6from easynetwork.protocol import DatagramProtocol
7from easynetwork.serializers import JSONSerializer
8
9
10async def main() -> None:
11 protocol = DatagramProtocol(JSONSerializer())
12 address = ("localhost", 9000)
13
14 async with AsyncUDPNetworkClient(address, protocol) as client:
15 print(f"Remote address: {client.get_remote_address()}")
16
17 ...
18
19
20if __name__ == "__main__":
21 asyncio.run(main())
Note
The call to wait_connected()
is required to actually initialize the client, since we cannot perform asynchronous operations
at object creation. This is what the client does when it enters the the async with
context.
Once completed, wait_connected()
is a no-op.
Using An Already Connected Socket
If you have your own way to obtain a connected socket.socket
instance, you can pass it to the client.
If the socket is not connected, an OSError
is raised.
Important
It must be a SOCK_DGRAM
socket with AF_INET
or AF_INET6
family.
Warning
The resource ownership is given to the client. You must close the client to close the socket.
1from __future__ import annotations
2
3import socket
4
5from easynetwork.api_sync.client import UDPNetworkClient
6from easynetwork.protocol import DatagramProtocol
7from easynetwork.serializers import JSONSerializer
8
9
10def obtain_a_connected_socket() -> socket.socket:
11 sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
12
13 ...
14
15 return sock
16
17
18def main() -> None:
19 protocol = DatagramProtocol(JSONSerializer())
20 sock = obtain_a_connected_socket()
21
22 with UDPNetworkClient(sock, protocol) as client:
23 print(f"Remote address: {client.get_remote_address()}")
24
25 ...
26
27
28if __name__ == "__main__":
29 main()
1from __future__ import annotations
2
3import asyncio
4import socket
5
6from easynetwork.api_async.client import AsyncUDPNetworkClient
7from easynetwork.protocol import DatagramProtocol
8from easynetwork.serializers import JSONSerializer
9
10
11async def obtain_a_connected_socket() -> socket.socket:
12 sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
13
14 ...
15
16 return sock
17
18
19async def main() -> None:
20 protocol = DatagramProtocol(JSONSerializer())
21 sock = await obtain_a_connected_socket()
22
23 async with AsyncUDPNetworkClient(sock, protocol) as client:
24 print(f"Remote address: {client.get_remote_address()}")
25
26 ...
27
28
29if __name__ == "__main__":
30 asyncio.run(main())
Note
Even with a ready-to-use socket, the call to wait_connected()
is still required.
Basic Usage
Sending Packets
There’s not much to say, except that objects passed as arguments are automatically converted to bytes to send to the remote host thanks to the protocol object.
1client.send_packet({"data": 42})
1await client.send_packet({"data": 42})
Receiving Packets
You get the next available packet, already parsed.
1packet = client.recv_packet()
2print(f"Received packet: {packet!r}")
You can control the receive timeout with the timeout
parameter:
1try:
2 packet = client.recv_packet(timeout=30)
3except TimeoutError:
4 print("Timed out")
5else:
6 print(f"Received packet: {packet!r}")
1packet = await client.recv_packet()
2print(f"Received packet: {packet!r}")
You can control the receive timeout by adding a timeout scope using the asynchronous framework:
1try:
2 async with asyncio.timeout(30):
3 packet = await client.recv_packet()
4except TimeoutError:
5 print("Timed out")
6else:
7 print(f"Received packet: {packet!r}")
Tip
Remember to catch invalid data parsing errors.
1try:
2 packet = client.recv_packet(timeout=30)
3except DatagramProtocolParseError:
4 print("Received something, but was not valid")
5except TimeoutError:
6 print("Timed out")
7else:
8 print(f"Received packet: {packet!r}")
1try:
2 async with asyncio.timeout(30):
3 packet = await client.recv_packet()
4except DatagramProtocolParseError:
5 print("Received something, but was not valid")
6except TimeoutError:
7 print("Timed out")
8else:
9 print(f"Received packet: {packet!r}")
Receiving Multiple Packets At Once
You can use iter_received_packets()
to get all the received packets in a sequence or a set.
1all_packets = [p for p in client.iter_received_packets()]
1all_packets = [p async for p in client.iter_received_packets()]
The timeout
parameter defaults to zero to get only the data already in the buffer, but you can change it.
1all_packets = [p for p in client.iter_received_packets(timeout=1)]
See also
UDPNetworkClient.iter_received_packets()
The method description and usage (especially for the
timeout
parameter).
1all_packets = [p async for p in client.iter_received_packets(timeout=1)]
See also
AsyncUDPNetworkClient.iter_received_packets()
The method description and usage (especially for the
timeout
parameter).
Advanced Usage
Note
This section is for people who know what they’re doing and are looking for something specific.
Low-Level Socket Operations
For low-level operations such as setsockopt()
, the client object exposes the socket through a SocketProxy
:
1client.socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, True)
1client.socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, True)
Warning
Make sure that wait_connected()
has been called before.
Concurrency And Multithreading
All client methods are thread-safe. Synchronization follows these rules:
send_packet()
andrecv_packet()
do not share the samethreading.Lock
instance.close()
will not wait forrecv_packet()
.The
client.socket
methods are also thread-safe. This means that you cannot access the underlying socket methods (e.g.getsockopt()
) during a write operation.
All client methods do not require external task synchronization. Synchronization follows these rules:
send_packet()
andrecv_packet()
do not share the same lock instance.close()
will not wait forrecv_packet()
.