Viewing video

[Hoof Hearted 0]

Sorry this is going to be complicated. My UK customer asked me to go out to China and install a CCTV system in his factory there. I used a Samsung SHR-5160 DVR. I did a port forwarding rule on the router there so that web traffic on the default Port 80 is sent to the DVR. The DVR also uses port 8000. I did another rule on the router to send this traffic to the DVR.

 

When I came back to the UK everything worked ok for a month, then we found that we could not log into the DVR remotely from the UK. However, the chinese office manager could see the video perfectly from his home in the same city. The chinese are famous for blocking various internet traffic (Great Firewall of China). I was immediately suspicious that they might have done something.

 

So I did another rule and moved the http traffic onto another port on the router. This allowed us to log into the DVR again, but when we look at the video we only see 3 seconds of motion before it freezes. The same also happens on playback. I tried various ports and got the same behaviour each time. The office manager still sees everything working perfectly at his home.

 

Has anyone got an idea of how I might fix this?

 

Ian

[tomcctv 187]

Sorry this is going to be complicated. My UK customer asked me to go out to China and install a CCTV system in his factory there. I used a Samsung SHR-5160 DVR. I did a port forwarding rule on the router there so that web traffic on the default Port 80 is sent to the DVR. The DVR also uses port 8000. I did another rule on the router to send this traffic to the DVR.

 

When I came back to the UK everything worked ok for a month, then we found that we could not log into the DVR remotely from the UK. However, the chinese office manager could see the video perfectly from his home in the same city. The chinese are famous for blocking various internet traffic (Great Firewall of China). I was immediately suspicious that they might have done something.

 

So I did another rule and moved the http traffic onto another port on the router. This allowed us to log into the DVR again, but when we look at the video we only see 3 seconds of motion before it freezes. The same also happens on playback. I tried various ports and got the same behaviour each time. The office manager still sees everything working perfectly at his home.

 

Has anyone got an idea of how I might fix this?

 

Ian

Hi Ian. port 80 will get blocked by some isp for inbound. and you also set a port to 8000. this will be classed as port 80. your best bet is to set up new ports around the 5555 mark i.e 5550. just remember to add this to your ip when you log in i.e http://yourip:5550

[Hoof Hearted 0]

In the configuration screeen, this DVR needs 2 ports need to be specified. I attached a screenshot to show this. The defaults are 80 and 8000. Both of these ports need to be opened in the router before the unit can be seen externally. The external login screen has boxes for username, password and port number. The port defaults to 8000. So it seems that it uses port 80 for http and 8000 for some other process.

 

Like I said, port 80 no longer works. I redirected incoming traffic on a different port to go to the router on port 80.

 

The video does work. But only for 3 seconds. If I select a different camera, that also works but only for 3 seconds. I created a new rule on the router directing incoming 5550 traffic to port 80 on the router. It made no difference. I can log in and browse around, but the video freezes 3 seconds after I select a camera to view.

[craiga 0]

Hi.

The 3 second problem can be related to interference by aggressive transparent caches. If you use port 80, 8080, 8000, 81, or 8081 externally (across any part of the Internet), then the likelihood of problems by transparent caches is significant. Don't use these addresses.

 

If you are connecting from an office network that has a proxy server, then the problem is highly likely to be the proxy server (and you can't fix the problem by changing the port). The solution would be for the administrator to disable caching for the IP address associated with the DVR within the proxy server itself.

-Craig

[Hoof Hearted 0]

If you read my original post, the 3 second problem only affects people logging in from the UK, from within China everything is ok. I just changed the 8000 port to 58000 and I changed the http port to 12345. Still got the freeze after 3 seconds viewing from the UK

 

I'm connecting from my home pc which is not using a proxy server. Other people have tried connecting using different ISP and office networks. The 3 second freeze is absolutely consistent.

 

Ian

[tomcctv 187]

In the configuration screeen, this DVR needs 2 ports need to be specified. I attached a screenshot to show this. The defaults are 80 and 8000. Both of these ports need to be opened in the router before the unit can be seen externally. The external login screen has boxes for username, password and port number. The port defaults to 8000. So it seems that it uses port 80 for http and 8000 for some other process.

 

Like I said, port 80 no longer works. I redirected incoming traffic on a different port to go to the router on port 80.

 

The video does work. But only for 3 seconds. If I select a different camera, that also works but only for 3 seconds. I created a new rule on the router directing incoming 5550 traffic to port 80 on the router. It made no difference. I can log in and browse around, but the video freezes 3 seconds after I select a camera to view.

thank for pic. your dvr port is the 8000 change that to 5555 and leave your http 80 port as it is. but you will have to portforward 5555 in your router. and then you should be ok using http://yourip:5555

[Hoof Hearted 0]

No that doesn't work. Let me explain.....

 

As described previously http://my_ip = Page cannot be displayed. Port 80 has not been working at all for the past few weeks. It used to work initially though.

 

I changed the port setting as you suggested but http://my_ip:5555 just gives 'Page cannot be displayed'

 

Dont forget I mentioned previously that I connect using the http port listed on that configuration screen. The login screen has boxes for username, password and port number.

 

My http port is currently 60081. So after changing the other port, the only way to login is by connecting with http://my_ip:60081 then on the login screen entering 5555 in the port number box. The video still freezes 3 seconds after I select a camera though. After it freezes I can still use the web interface for all other functions.

 

Ian

[rory 0]

How is the upload bandwidth speed from the DVR location?

More then likely the chinese ISP is filtering outgoing traffic like mad.

[craiga 0]

Hi.

Try changing port 8000 to 143 (imap) or 110 (pop3) or 23 (telnet). It's not likely these ports are outright blocked by the authorities because they are in such high use (although it's not out of the question they could still be filtered).

 

The chinese do force connections on HTTP to drop when a keyword is transmitted that the government doesn't like -- it's possible they do this on all TCP traffic -- in which case it's a huge problem if the protocol on default port 8000 contains an innocent keyword that's (now) banned. It certainly would explain what you are seeing.

 

Setting up a VPN would get your traffic out of China unscathed, but whether or not this is a useful solution for you depends on where you want to access it...

-Craig

 

PS: transparent proxies won't necessarily affect all locations equally, so just because it can be accessed within China is no indicator that transparent proxies are not involved. But since you've changed ports away from the eighties and still have the problem, it's very unlikely to be the problem.

[Hoof Hearted 0]

I tried changing the DVR port to 143, but it told me I must use a port number greater than 2000. Can't imagine why that would be.

 

The really strange thing about all this is that I no matter what permutation of ports I use, I always see 3 seconds of video before it freezes. I can select another camera subsequently and see another 3 seconds. Because I can repeatedly get 3 second bursts of video, i'm not so sure about it being blocked. The caching suggestion sounds more likely to me.

 

To be clear about this, several of us have tried to access the DVR from within different environments in the UK. We all see exactly the same.

 

We all log into a Server 2003 Terminal Server at the same site. That works fine. Plenty of bandwidth.

[rory 0]

How is it working on their local network?

[Hoof Hearted 0]

It works perfectly on the local network and it works perfectly when the office manager logs in from his home.

[craiga 0]

Hi.

Well you are not supposed to use ports under 1024 for this purpose, so preventing you from using ports under 2000 isn't really surprising. Keeps you from causing trouble by using well known ports like 143

 

Anyway, whatever port you are using for 8000 -- did you try forwarding both TCP and UDP on this port? I can't work out an argument that would explain what you are seeing as a result of not forwarding UDP packets, it is very possible this is a problem though...

 

Also, have you looked for any logs on the DVR? These might provide some info.

 

Anyway if forwarding UDP doesn't work, get a copy of wireshark ( http://www.wireshark.org/ ) and analyse what's happening. It will give you more clues.

 

If the traffic on port 8000 is UDP -- then the situation can be explained by traffic being blocked in one direction only -- the server doesn't get any indication that you are still connected and so quits sending video.

 

The other thing is that if the traffic is TCP, the Chinese do send forged TCP resets (RST) to both ends when they want to block traffic -- they actually allow the connection to initiate, and then block it because they don't like the content (some ISPs use the same to prevent some peer-to-peer technologies). You'd also see TCP resets if your ACKs weren't being received (high packet loss or blocked in one direction after the connection was initiated).

 

Both problems would explain the 3 seconds of video and then nothing.

 

Running wireshark at the other end will provide more information, but bear in mind the situation is more complicated; see:

http://wiki.wireshark.org/CaptureSetup/Ethernet

for details.

 

-Craig

[Hoof Hearted 0]

Hi yes I am port forwarding UDP and TCP packets in the router. I think the router must be set correctly because the office manager can see continuous video in his home in the same chinese city. I got him to check again that it's ok today.

 

The logs on the DVR seem quite basic and dont give me any information about networking issues.

 

I tried that wireshark link you sent me, but it appears to be a dead link for me.

 

Ian

[craiga 0]

Hi.

Wireshark's the only way to go then. Not sure what happened to their website -- try back in a bit, it's not working at the moment...

-Craig

[tomcctv 187]

It works perfectly on the local network and it works perfectly when the office manager logs in from his home.

Hi Ian.

what happends when you log on with 3g modem i.e vodafone, from the uk. just to see if it still has its problem

[Hoof Hearted 0]

I dont have one of those myself, but one of the other UK guys has an Iphone. I'll ask if he can login using that.

[Hoof Hearted 0]

I've had an email from the office manager in China. He made some enquiries and it turns out that the chinese government imposed a complete block on port 80 around the time we started having this problem. If it's only on port 80, that doesn't explain why we get the freezing on other ports. The office manager has made an application to get port 80 unblocked on our IP address.

 

Ian

[tomcctv 187]

I dont have one of those myself, but one of the other UK guys has an Iphone. I'll ask if he can login using that.

hi ian.

you will not get it on a iphone. it needs active x which iphones dont have. the reason why i say to try 3g is it is not blocked in china. just wanted to see if it still had the problem.