I have a very basic doubt regarding web application url.
Suppose a web application is running locally on my machine.
Will there be any difference in the response time if I access the application using below two url ?
http://localhost:8080/SomeApplicationContext
http://hello:8080/SomeApplicationContext -- Assuming my machine name is hello
depends on whether or not you have hello in your hosts file. (same place where localhost is defined) if its not, then yes because your computer will have to check with DNS before it can access the resource, in which case the difference will close to the round trip latency of that request.
No difference, You can run the script/coding using http://localhost:8080/SomeApplicationContext from your own machine only, if you like to run this program from other pc/system you can use the http://hello:8080/SomeApplicationContext url ( you can run this url from your own machine also).
I hope this is perfect.
no. Why would that be? Response time depends on servers ability to serve the content -- that is latency in processing teh request and the other is network latency. In your case both are the same. So, no difference.
localhost or hello, both of them must be defined in your hosts file. Your OS looks to hosts file (such as /etc/hosts in many Linuxes or %windir%/system32/drivers/etc in some Windowses) if it cannot find it in there, OS asks a DNS server for server ip.
In your situation, both must be defined in your hosts file. No change in network latency.
But if you mean different domains pointing same IP, then it depends on how your server application (apache, nginx, IIS etc.) handles different domain names.
Related
I'm currently developing a Wolkenkit application which is run on my local machine.
I want to upload a file from the Wolkenkit app to the blob server (as documented here).
When sending a POST request from the server to https://local.wolkenkit.io:3001/, Node.js gives me the error ECONNREFUSED.
I've tested the POST-Request with another program and it works there. Any idea why it doesn't work from the wolkenkit application itself?
Thanks!
The Storing files sample you linked to shows code that is to be run in the browser, not in the backend itself. Of course, both should work, but there are a few minor differences you need to watch out for.
Fixing the host name
First, I suppose that local.wolkenkit.io in your case maps to 127.0.0.1, which is the default for wolkenkit. That means that when you try to connect to this domain from within a Docker container, the container does not try to call out to the blog storage container, but it stays within itself. So, the first thing that needs to be fixed is the host name.
Basically, there are two options for this: You can either setup local.wolkenkit.io so that it resolves to the external IP address of your machine. This would work, but is pretty cumbersome. The other option is to directly address the appropriate container that is responsible for blob storage, by its internal name. The internal name is <name-of-your-app>-depot-file. So you need to replace https://local.wolkenkit.io:3001/ by https://<...>-depot-file.wolkenkit.io:3001/.
Fixing the port
Second, the port is wrong. This is because the blob storage service is internally running on port 3000, externally on 3001. So instead of https://<...>-depot-file.wolkenkit.io:3001/ you need to use https://<...>-depot-file.wolkenkit.io:3000/.
Once you have done this you should not get any more errors like ECONNREFUSED, since now the service can be found.
Fixing SSL issues
Third, since you are now connecting to the blob storage service using a different domain name, the SSL certificate doesn't match any more, since it was issued for local.wolkenkit.io. As a result, you will get SSL errors when trying to connect.
The simplest way to get around this is to disable any SSL checks (albeit this is also the most insecure way to handle this!). How to do this depends on the HTTP client module you are using. E.g., in request there is an option called strictSSL that you can set to false.
Of course, what you actually should do is to either use a custom certificate which includes this domain name as well, or to write a function that handles the certificate check and accepts the presented one, especially in this case.
If you do all of this, things should work :-)
PS: I am one of the authors of wolkenkit. Thanks a lot for bringing up this issue, and we will take care of this in the future, to make storing blobs easier.
I am working with a Synology NAS type aDS716+II, DSM 6.1.4-15217 Update 2 on wich runs Docker with a Jira container.
So now what I want to do I'm assinged to get to work is to access Jira's webinterface with let's say jira.synology.local with synology being the servername.
I read a lot about nginx and how it's built in since DSM 6.X but I don't seem to get it to work properly at all.
I can access Jira's webinterface from another machine within the LAN via IP_OF_SYNOLGY:PORT so when setting up a reverse proxy on the server it should be pointing to LOCALHOST:PORT right? I have also tried using the actual IP instead of LOCALHOST but without success.
I can access the interface of Synology itself not only via IP_OF_SYNOLGY:PORT but also via DOMAINNAME.LOCAL if I set the domain name.
I really don't know what I'm missing and I tried everything I could think of. Does someone has experience with this?
If some information is missing, I'll gladly provide it. I'm fairly new to synology I have to admit. Thanks in advance!
So this has gotten zero response but I figured probably someone will have a similar "problem" in the future, so I will answer anyway.
I solved everything, when I setup Active Directory. When installing AD, the DNS-Server will automatically be installed too.
So we have JIRA running in a Docker container (on port, let's say, 12345) and I want to access it via the LAN on jira.domainname.
To do so we need to have installed DSM6.X or higher (for nginx) and the DNS-Server. That's it.
In the DNS-Server you will have to create a new master zone
and apply the following settings, whereas you can freely choose the domain name and Master DNS server must be the IP of your synology station, since it functions as a DNS
Then you want to edit the Resource Record
There you want to add an A Record Resource
and an CNAME Record Resource
So your Resource Records will look like this
Now the last step for setting up the DNS server is to tell it what to do if there is no specific record for a query. So for example if you want to open jira.domainname in your browser, there is a specific record for that and the DNS server knows how to direct it. But if you want to open up for example google.com the DNS server has no information on that and does now know what to do. So what we do now is to to tell the DNS server to forward the request, if it has no records for a request. To do so, enable the forwarders and put in the IP of your gateway/ managed switch as primary and some public DNS server (8.8.8.8 for one of google's DNS server) as secondary.
Please remember that jira.domainname shall always be the domainname you choose and 192.168.0.200 shall always be the IP of your synology station.
So now the DNS server is completely setup. Now we want to take advantage of the built-in reverse proxy (which runs on nginx in the background). To do so we navigate as seen here
and create a new reverse proxy rule
So now that the URL's can point to the same destination (your synology, 192.168.0.200) but on different Port. That comes in very handy for some applications running in docker.
So now if you are running this in an home setup or small office, you probably are working with standard issue commercial router such as for example a FritzBox by AVM. Those are pretty good but beware that some prohibit the so called DNS Rebinding which means that DNS requests pointing to a local IP will be not allowed. Since in this setup the DNS server (your synology) and the destination JIRA (also your synology) are in the same LAN, we have to create an exception. Probably other routers don't suppress those requests, but if so exceptions are necessary.
So the next step, it to tell your Gateway or managed switch that it has to use the newly setup DNS server as the primary DNS server. For FritzBox' you can do so here
put in the IP of your DNS server and an secondary DNS server. This is important as a fallback solution if your DNS server probably stops working at some point.
Now that everything is setup I would recommend to restart the router/ managed switch, synology and the workstation you are working on, to flush all caches. After that you can simply open your browser and type in jira.domainname and JIRA should open up. You can also open a terminal/ cmd and type in nslookup jira.domainname to see if it is being resolved correctly.
I really hope this will help someone at some point and if there are any additional questions, please feel free to comment this or write me directly!
I'm trying to figure out how these all work together, and there are bits and pieces of information all over the internet.
Here's what I (think) I know:
1) When you enter a url into your browser that gets looked up in a domain name server (DNS), and you are sent an IP address.
2) Your computer then follows this IP address to a server somewhere.
3) On the server there are nameservers, which direct you to the specific content you want within the server. -> This step is unclear to me.
4) With this information, your request is received and the server relays site content back to you.
Is this correct? What do I have wrong? I've done a lot of searching over the past week, and the thing I think I'm missing is the big picture explanation of how all these details tie together.
Smaller questions:
a) How does the nameserver know which site I want directions to?
b) How can a site like GoDaddy own urls? Why do I have to pay them yearly fees, and why can't I buy a url outright?
I'm looking for a cohesive explanation of how all this stuff works together. Thanks!
How contents get loaded when I put a URL in a browser ?
Well there some very well docs available on this topic each step has its own logic and algorithms attached with it, here I am giving you a walk through.
Step 1: DNS Lookup : Domain name get converted into IP address, in this process domain name from the URL is used to find IP address of the associated server machine by looking up records on multiple servers called name servers.
Step 2: Service Request : Once the IP address is known, as service request depending on protocol is created in form of packets and sent to the server machine using IP address. In case of a browser normally it will be a HTTP request; in other cases it can be something else.
Step 3: Request handling: Depending on the service request and underlying protocol, request is handled by a software program which lives normally on the server machine whose address was discovered in previous step. As per the logic programmed on the server program it will return a appropriate response in case of HTTP its called HTTP Response.
Step 4: Response handling: In this step the requesting program in your case a browser receives the response as mentioned in the previous step and renders it and display it as per defined in the protocol, in case of HTTP a HTTP body is extracted and rendered, which is written in HTML.
How does the nameserver know which site I want directions to
URL has a very well defined format, using which a browser find out a hostname/domain name which is used in turn to find out the associated IP address; there are different algorithms that name-servers runs to find out the correct server machine IP.
Find more about DNS resolution here.
How can a site like GoDaddy own urls? Why do I have to pay them yearly fees, and why can't I buy a url outright?
Domain name are resources which needed management and regulation which is done ICANN they have something called registries from which registrar(like GoDaddy) get domains and book them for you; the cost you pay is split up between ICANN and registrar.
Registrar does a lot of work for you, eg setup name server provide hosting etc.
Technically you can create you own domain name but it won't be free off course because you will need to create a name server, need to replicate it other servers and that way you can have whatever name you want (has too be unique); a simple way to do that is by editing your local hosts files in linux it is located at /etc/hosts and in windows it is located at C:\Windows\System32\drivers\etc\hosts but its no good on internet, since it won't be accepted by other servers.
(Precise and detailed description of this process would probably take too much space and time to write, I am sure you can google it somewhere). So, although very simplified, you have pretty good picture of what is going on, but some clarifications are needed (again, I will be somewhat imprecise) :
Step 2: Your computer does follow the IP address received in step 1, but the request set to that IP address usually contains one important piece of information called 'Host header', that is the actual name as you typed in your browser.
Step 3: There is no nameserver involved here, the software(/hardware) is usually called 'webserver' (for example Apache, IIS, nginx etc...). One webserver can serve one or many different sites. In case there are more than one, webserver will use the 'Host header' to direct you to the specific content you want.
ICAAN 'owns' the domain names, and the registration process involves technical and administrative effort, so you pay registrars to handle that.
I know in airports, for example, I've connected to their AP, and it pops up a browser window to log in on my device. Is it possible to do so with NodeMCU in lua, or even with c firmware?
This can accomplished by setting the DNS server for a connecting client [via DHCP] to a sort of DNS proxy. It doesn't need to be a fully featured DNS server, it only needs to be able to either return a static DNS answer for any host name query or forward the request to a real DNS server, to resolve host names as usual.
The static answer effectively hijacks web requests at the DNS level, by forging the DNS answer, causing all host names to resolve to the IP address of a local web server. That local web server ignores any Uri details and serves a login prompt for every request. It must also maintain a list of client MAC addresses that have authenticated.
NodeMCU does have a built-in DHCP server, as part of it's built-in WiFi AP, but running both a web and a DNS proxy in ESP8266's limited memory would be a hell of a trick. I think that two of them working cooperatively, interfaced using the SPI bus might be workable... maybe even three of them, one dedicated to maintaining the list of authenticated MACs, expiring them, etc.
Note that the only part of this I have done on an ESP 8266 is some very simple web server functionality, so it's mostly theory. If you try it I'd be very interested in hearing about it. :-)
You might want to try out CaptiveIntraweb project (https://github.com/reischle/CaptiveIntraweb) which is based on NodeMCU.
There is also thread (http://www.esp8266.com/viewtopic.php?f=32&t=3618) on ESP8266 community forum that discusses the solution details.
I am accessing 2 URLs. The domain name/server part is the same. The resource part is different.
The URLs are like the following:
https://aa.bb.com/dir1/dir2
https://aa.bb.com/dir3
When I access the first URL, I get redirected to the second URL. Is it possible that the second URL be hosted on a different web server than the first or both resources would be on the same web server?
If by web server you mean physical computer, absolutely they could be on different servers. Google and Akamai, among others, have large collections of machines serving the same domain names. It helps with speed, since you are likely to receive pages from a server near you.
In general, it does not appear to be possible to reliably tell whether you are talking to the exact same server before and after a redirect. First, it is difficult to test for IP addresses from a Web page (see, e.g., this question and this one). Second, even if the IP addresses are the same before and after the redirect, they may be on different machines. For example, TCP anycast can change which server you are talking to without changing the IP address. Also, network address translation and load-balancing may change which server you are talking to behind a firewall, which you would probably have no way of finding out unless the server provided some ID of its own.