I am now writing a program which should be able to dynamically select and switch 802.11 channels. Multiple threads can use a shared 802.11 radio. The goal is to let a thread lock the radio before switching channel, and then transmit one data packet, finally, unlock the radio after the data packet has been successfully transmitted out of the 802.11 NIC or dropped permanently.
But I can't find a way to know if a data packet has been transmitted out of the NIC card or it is still somewhere in the host. I am programming in C on Ubuntu. I use UDP socket to send the data packet. A successful return from "sendto" doesn't indicate that the data packet has been successful transmitted out of the hardware.
Could anyone point out a way to receive notifications of packet delivery status from 802.11? To sum up, I want to receive notifications when a data packet has been transmitted out of the NIC for broadcasting mode, and when a data packet has been successfully received by the other end or has been permanently dropped for unicast mode.
Any answer will be appreciated!
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My app send message to server then wait for reply, over udp. But there are random packet loss.
I want to detect packet loss by timeout, how can I do it in swift?
I cannot find it from doc.
I developed a C++ app to stream video from a webcam on an Odroid device over UDP. The client is an iPhone app using simple UDP sockets and it works perfectly over Wi-fi, but not over LTE. The sendto() call works okay, but the recvfrom() blocks forever. First I thought it has to do with iPhone blocking UDP traffic, but I also tried a client on my laptop connected in the iPhone's hotspot and thus over LTE.
Do you think there is something with phone providers blocking UDP traffic?
I preferred UDP instead of TCP for faster streaming.
Any advice would be highly appreciated!
Thanks!
UPDATE: I found the cause of the problem after some further inspection. It turns out that UDP over LTE sets the IP_MTU_DISCOVER flag and if the user's packet is larger than the device's MTU, it does not perform IP fragmentation but simply drops the packet. My application is sending packets larger than MTU, but in the case of Wi-fi they are fragmented in the IP layer. If you disable the IP_MTU_DISCOVER flag, the large packet is fragmented and arrives successfully in the destination. The other alternative would be to send packets smaller than MTU from the application. Both approaches do not perform that well, but at least the mystery is solved.
I am new to socket programming and don't have much idea on how it works, Here is the use case, Im developing an iPhone app, where users stream real time audio originated from another iPhone device (in short Multi casting)
What I have done so far:
I opened a port on server which keep listening to incoming data from clients. On the iOS side, i implemented methods thats read the packets received on the server and process it accordingly (i have used GCDAsyncSocket)
Problem where I need help:
The above use case works perfect for 2 users, one that sends the audio data to the server and the other one reads that data to play audio. But actually there would not always be a single user originating audio data, they could be more than 100+, Now when all of them are sending different audio data to server how could i filter data for the listeners that everyone receive only there data, I overcome this problem adding a token on every packet like
unique_token:<ffdefa09 fedead3...... //Audio Data
But this process is way too slow as every client is listening all the packets and only process the ones with the token they are assigned.
Is there anyway, we can make a peer to peer connection by which the originating device become server and only sends data to its listeners and don't bother anyone else?
Can't you add something like a light protocol before you start steaming audio data to server ?
iPhone -> server [Request: Start Stream Audio]
server -> iPhone [OK: TCP Port:4444]
// iphone sending audio packets to port 4444
iPhone2 -> server [Request: Start Stream Audio]
server -> iPhone2 [OK: TCP Port:4445]
then the server can filter all audio channels with TCP port ID instead of packet ID (or maybe I misunderstood your issue)
Btw I don't think you can do any "real" P2P with iPhone on cellular networks because of providers firewalls
for every end who send the audio data, you create a socket and recv audio data, and for every end who receive the audio data, you create a socket and send audio data.
P2P is lots of work , because many device are behind the public address.
You need to separate your command data from your streaming/audio data.
First you need the iphones to tell the server what they want,
iphone 1: "i want to stream this data with id 1"
iphone 2: "i want to listen to stream with id 1"
that way the server can tell the iphone where to connect for getting the data it needs, as HaneTV suggested with port numbers
I am building a iPad app (Object C) and its pure purpose is to receive information from a wireless device. I can connect fine and receive information but sometimes the incoming stream has information I don't want. Is there a way to flush the incoming stream to clear all incoming bytes?
No, there isn't. Just skip it.
I need to receive data periodically through a BlueTooth External Accessory.
I implemented an event-driven model of EA's streams. However, the initial transmission from bluetooth is always delayed. For example, if each packet was 15 bytes long, the stream delegate would not fires until about 150 bytes.
Will polling help?
EDIT:
Also I found it hard to recover the session after the app switching back from background to foreground. Trying to open session again would fail. Any idea?
Read every bytes when NSStreamEventHasBytesAvailable arrives.
Did you develop your own Bluetooth accessory? May be the MCU only flushes after sending every 150 bytes.
Also you mentioned initial transmission. Do you know once the Bluetooth device is paired and connected to iPhone, it has to go through some identification process, handshaking some secret certificate. This may take few and even 10 seconds, depending on signal quality. This may be the cause of delay.