From
Link: www.w3.org/TR/webrtc/#dom-rtcbundlepolicy
Content: 4.2.5 RTCBundlePolicy Enum
"If the remote endpoint is bundle-aware, all media tracks and data channels are bundled onto the same transport."
When is an endpoint bundle-aware and when not? And what does bundle-aware means?
To establish a p2p connection, WebRTC will allocate and do STUN network checks on up to 3 ports (multiplied by ways they can be reached) on either end, and as they're discovered (which takes time), ask JS to trickle-exchange info on each of these "ICE candidates" across a signaling channel, once for video, once for audio, and once for data (if you have it).
WebRTC does this mostly to support connecting to non-browser legacy devices, because all modern browsers support BUNDLE, which is when all but one candidate end up being thrown away, and all media gets bundled over that single port.
WebRTC even has a "max-compat" mode that goes even further, allocating a port for each piece of media, just in case the other endpoint is really old.
WebRTC doesn't know the other endpoint is a browser until it receives an "answer" from it, but if you know, you can specify "max-bundle" and save a couple of milliseconds.
I have a couple of questions regarding Unix Domain Sockets. We currently have an application that has a receiver service receiving datagram packets from multiple client processes on the same machine using the loopback address. We want to convert it over to using Unix Domain Sockets. Here are my questions:
The receiver process may be down when senders are running, in UDP, the packets were just dropped. Is the behavior of UDS the same or do the senders receive an error (may also have started before the receiver and therefor the UDS path may not have been bound)?
The receiver may go down and be restarted. Since it has to unlink the path before binding, do the running senders packets make it to the receiver or do they need to reset?
If the receiver is down for an extended period, do the oldest packets get dropped or will it fill blocking the senders?
Short story: My DDS subscriber cannot see data from my DDS publisher. What am I missing?
Long story:
QNX 6.4.1 VM A -- Broken Publisher. IP ends with .113
QNX 6.4.1 VM B -- Working Publisher. IP ends with .114
Windows 7 -- Subscriber/Main Dev box. IP ends with .203
RTI DDS 5.0 -- Middleware version
I have a QNX VM (hosted on the network, not on my machine) that is publishing some data via RTI DDS. The data never shows up in my Windows 7 subscriber application.
Interestingly enough, I can put the same code on VM B, and the subscriber gets data. Thinking this must be a Windows 7 firewall issue, I swapped VM A's IP address with VM B, but this did not help.
Using Wireshark, I can see some heartbeat traffic from VM A, but no data. From VM B, I see the heartbeat traffic and the data. Below is a sanitized Wireshark snippet.
NDDS_DISCOVERY_PEERS is set to include both multicast and the explicit IP address of the other side of each conversation. The QOS profiles are the same, and the RTI Analyzer indicates the Match Analysis was successful (all green).
VM A:
NDDS_DISCOVERY_PEERS=udpv4://239.255.0.1,udpv4://127.0.0.1,udpv4://BLAH.203
VM B:
NDDS_DISCOVERY_PEERS=udpv4://239.255.0.1,udpv4://127.0.0.1,udpv4://BLAH.203
Windows 7 box:
NDDS_DISCOVERY_PEERS=udpv4://239.255.0.1,udpv4://127.0.0.1,udpv4://BLAH.113,udpv4://BLAH.114
When I include them in the NDDS_DISCOVERY_PEERS line, other folks on the network can see DDS traffic from VM A with DDS SPY on their Windows 7 box. My Windows 7 box can not.
Windows 7 event log does not appear to show any firewall or WFP stopping the data packets.
RTI DDS Spy run from my Windows 7 machine shows that VM A (0A061071) writers are visible on the network, but no data is being received. It also shows that the readers in my subscriber on my Windows 7 machine are visible, though it shows up at an odd IP address.
Bonus question (out of curiosity only, NOT the primary question): why does traffic on my local machine show up in DDS SPY as 192.168.11.1 instead of my machine's IP or even 127.0.0.1?
Main Question: What am I missing?
Update:
route print on my Windows 7 box appears to show that I have joined a multicast group with VM A.
netsh interface ip show joins seemed to concur.
Investigation Update:
I rebooted the VM to no effect.
I rebooted the Windows box to no effect.
I removed the multicast from the NDDS_DISCOVERY_PEERS environment
variables on both sides to no effect.
The Windows 7 box has three network interfaces (plus loopback): 1
LAN connection and 2 (unrelated) VM adapters. We are working with
the LAN connection. The QNX VM has one network interface (plus
loopback). Note that the working VM and the broken VM use a
different ethernet driver than each other, as they are slightly
different flavors of QNX 6.4.1. The broken one has wm0 as the
interface, and the working one has en0 as the interface. I don't believe this is the issue, but it is a difference.
I ran DDS SPY on the "broken" QNX VM while it was playing back, and
I got DDS data. I don't have a good method to sniff the network
between where the VM is hosted and my Windows 7 machine to see if it
makes it out of the interface, but looking at the transmitted packet
count out of the ethernet interface on the QNX VM indicates that it
is definitely transmitting something, and the Wireshark captures on the Windows 7 machine itself show that at least some traffic is making it through.
Other folks on the LAN here can see the DDS traffic from the
"broken" VM, which leads me to believe it is a Windows setup issue,
rather than a broken VM--I just can't see what it could be. I've
re-checked the firewall, to no avail. I would have thought that if it were a firewall issue, the problem would have gone away when I swapped IP addresses between VM A and VM B. In any case, the Windows 7 firewall is currently off, to no avail.
Below are several screens of Wireshark output. I skipped a bunch between the third and the fourth, as after the fourth, the traffic tended to look like the bottom of the fourth until the end.
(Skipped a bunch here)
(Pretty much continues on like the last 11 lines above)
What else should I try?
Update:
To answer Rose's question below, using rtiddsping -publisher on the bad VM and rtiddsping -subscriber works appropriately.
I wonder if this issue is caused by the weird IP address. The IP address it happens to publish and somehow latch on to is a local VM ethernet adapter (separate from VM A). See the screenshot below.
The address I would like it to attach to is 10.6.6.203. Any way I can specify that?
More than a year later this happened to me again with a different virtual machine. I had it working yesterday, so I was very suspicious. I scoured all my code changes for the past 24 hours for issues, but didn't find any. Then I decided to see if IT had pushed any patches to my computer.
Guess what? The Windows Firewall had been aggressively updated since the day before. Rules missing or changed, etc. The log said packets were being dropped. I opened the firewall filters up a bit, and suddenly, everything worked again. I hesitate to close this issue, as I am not 100% this was exactly the same as last year, but it feels very similar. I suspect that last year the settings in the firewall were not logging the packet drops.
Long and short of it: if DDS suddenly stops working, check your firewall settings.
A couple of things to try:
Try running rtiddsping -publisher on the broken VM and rtiddsping -subscriber on Windows. This has two advantages:
The data type is small and well-known, so if there's some problem with the data being fragmented due to the different Ethernet drivers, it will not happen with rtiddsping, and may help track down the problem.
Rtiddsping prints out when the publisher and subscriber discover each other, so you will be able to confirm that discovery is completing correctly on both sides. I am guessing discovery is working, because Analyzer is showing both applications, but it is good to confirm.
If you see the same problem with rtiddsping that you see with your application, increase the verbosity to rtiddsping -verbosity 3, and then 5. At the highest verbosity level, this will print (a lot of) additional output, which may give us a hint about what is happening.
To answer your bonus question about spy: The reason why spy is showing that IP address is because that is one of the addresses that is being announced as part of discovery. During discovery, a DomainParticipant can announce up to four IP addresses that can be used to reach it. Spy will choose one of those to display, but it may not be the actual address that is being used to communicate with the application. If your machine does not have any interface with the 192.168.11.1 IP address, this could indicate a larger problem. (This may be normal, though - as long as the correct IP is one of the four that are announced.)
Looking through the packet trace images, there is nothing that is obviously the problem. A few things I notice:
There seems to be a normal pattern of heartbeats/ACKNACKs in the final packet trace image. This indicates that there is some bidirectional communication between the two applications.
It is difficult to tell from these images whether the DATA being sent from .113 to .203 consists of participant-to-participant messages, or real discovery messages - except for two packets: packet #805, and packet #816 (fragments 811-815) look like discovery announcements that are being sent to .203. This indicates that you have at least four entities (DataWriters or DataReaders) in your application on .113.
So, discovery data is being sent by the application on .113. It is being received and reassembled by WireShark, but that doesn't always mean it was received correctly by the application.
Packet #816 has a heartbeat on the end of it. It is possible that packet #818 or #819 might be the ACKNACK that is responding to that heartbeat, but I can't be sure from the image. The next step is to look at those ACKNACKs from .203 to .113 to see if .203 thinks it has received all the discovery data. Here is an example of a HB/ACKNACK pair where a discovery DataReader has received all data:
Submessage: HEARTBEAT
...
firstSeqNumber: 1
lastSeqNumber: 1
The heartbeat sequence number is 1, which indicates it has only sent an announcement about a single DataReader.
Submessage: ACKNACK
...
readerSNState: 2/0:
bitmapBase: 2
numBits: 0
The readerSNState is 2/0, meaning it has received everything before sequence number two, and there is nothing missing. If there is something other than a 0 in the bitmap, it indicates the DataReader did not receive some data.
If you can confirm that the application is receiving all the discovery data correctly, it will be helpful if you can use a WireShark filter to show only user data, since the images aren't highlighting discovery vs. user data.
WireShark filter for just rtps2 user data:
rtps2 && (rtps2.traffic_nature == 3 || rtps2.traffic_nature == 1)
We had a similar issue with this. Here is the environment in a very summarized way:
A publisher
A working subscriber (laptop)
A non-working subscriber (desktop)
Both subscribers held exactly the same software (the desktop was a clone from the laptop, through Clonezilla), but rtiddsspy was blind from the desktop point of view; however, the opposite way worked well: the publisher machine's rtiddsspy saw the desktop. Laptop and publisher machines' always worked well. Laptop and desktop too (they saw each other's subscriptions)
The workaround for this (based on https://community.rti.com/content/forum-topic/discovery-issues) was to increase the MTU on the desktop NIC. Don't ask me why, but it worked.
EDIT: At the beginning, the MTU in the publisher was set to a higher value than the subscriber. So, we changed the MTU in the subscriber to match the publisher's.
I'm almost completely done with and iOS client for my REST service. The only thing I'm missing is the ability for the client to listen on the network for a UDP broadcast that receives the host display name and base URL for uploads. There could be multiple servers on the network broadcasting and waiting for uploads.
Asynchronous is preferred. The servers will be displayed to the user as the device discovers them and I want the user to be able to select a server at any point in time.
The broadcaster is sending to 255.255.255.255 and does not expect any data back.
I am a beginner in objective c so something simple and easy to use is best.
I recommend looking at CocoaAsyncSocket. It can handle UDP sockets well. I haven't tried listening to a broadcast with it, but it's probably your best bet.
"Because winpcap sends and receives data independent of host protocol such as TCP/IP, which means winpcap can't stop, filter and take control of other applications on the same machine control, it can only monitor them simply, so it can't provide support for similar network flow control, the quality of service, personal firewall and so on."
In this passage, what "winpcap can't stop, filter and take control of other applications on the same machine control" means?
It means that if some program on your machine is sending and receiving packets, the path those packets take through the operating system does not, and cannot, go through WinPcap; all WinPcap can do is listen to see copies of the packets sent and received by the machine.
This means that if you want to, for example, implement a firewall program to prevent other programs from connecting to particular addresses or ports or receiving connections from particular addresses or ports, or to modify packets sent by other programs before they get put onto the network or modify packets received from the network before they get passed to other programs, or do something else "active", you cannot use WinPcap.
WinPcap uses mechanisms in Windows that are intended to support programs such as packet sniffers, so that limitation is inherent in WinPcap; a library to support writing firewalls and the like would have to use different mechanisms in Windows (and those mechanisms might not support programs such as packet sniffers).