I am aware of how many times this has been asked based on searching StackOverflow, but I am still hoping someone could tell me whether I am wrong...
I am creating a peer-to-peer chat app for the iPhone. My initial idea was to avoid using a server, so Bonjour came to mind. I was happy coding for quite a while and implemented a lot of fancy features, but two days ago I started testing with two clients from different subnets and found that the clients couldn't connect to each other! I suddenly realized that Bonjour is meant for local networks and that a DNS server is necessary for wide area service broadcasting. Do I really need a server for Internet peer-to-peer chat? Are there any other options that do not involve using a server on the iOS platform?
I am wondering how you can do a chat app without using a server. There are many cheap solutions out there, Amazon has its own service, Google does as well. You can try first without even having to pay a cent.
I found the following from apple developer guide. This should answer your question -
Does Bonjour work between multiple subnets?
Yes. The first release of DNS Service Discovery (DNS-SD) for Mac OS X concentrated on Multicast DNS (mDNS) for single-link networks because this was the environment worst served by IP software. Starting in Mac OS X 10.4, Bonjour now uses Dynamic DNS Update (RFC 2316) and unicast DNS queries to enable wide-area service discovery.
To answer the question, the only way is for you to carry a list of all possible participants, and their current IP address, and for each possible participant to report to all others each time their IP Address changes. So, if you have 100 possible participants, then you must tell 99 others when your IP Address changes, and those 99 must tell you when their IP Address changes.
Bonjour may work on a LAN, a WAN or even a WAN, but it will never work on the internet.
The role of the server is so that each end point only need to tell one end point (the server) when it changes. My advice is get a cheap internet host, with a basic PHP / MySQL capabilities, and write yourself a very simple script to post and get user identities.
Related
I need to make TCP based decentralised chat app for local network. By decentralised I mean there is no central server. Each entity on a network should have server/client architecture. When app starts it should check which user is online ( already running the app ). My question is how can i check that? Can i do it by trying to connect via connect() function from socket library? I'm new to programming, especially socket programing, so if it's a dumb question sorry in advance.
You should definitely study how other decentralized applications do this. There are lots of techniques.
Each instance of the application should, as part of its server functionality, track the addresses of other instances of the application. Each instance should, as part of its client functionality, keep track of a few instances it can connect to. Prefer instances that have been around for a long time.
The software should include a list of servers that have been running for a long time and are expected to typically be available. You may wish to include a fallback method such DNS, maintained by anyone willing to keep a list of well-known servers offering access through a well-known port. The fallback method can also be IRC or HTTP.
If you want to stay decentralized, you might want to try multicasting or broadcasting a request packet to all hosts on the network to discover other instances of your chat application.
Something similar has been implemented in Pidgin, named Bonjour. It works quite nicely and provides chatting capabilities on a local network. More specifically, it is defined as a Serverless Messaging part of XMPP.
If you are looking for code examples, have a look at one of my projects where I use multicast to discover hosts on the local network that provide a specific service: Headers and implementation.
I am a PHP coder but not a server expert so I wondered if anyone could answer the following query.
Is there a way that a bot can determine the IP of my server when it runs through Cloudflare?
Someone suggested that folk could try ftp.domain.com and things like that. I do not have that setup on my server although Cloudflare do set this up automatically for you when you register a domain.
If you are a server expert and wanted to determine the actual IP of a server, how would you go about it?
Thanks.
PS: I do not want my IP public, hence the question.
Someone that really wants to find your server IP address probably can. We're only going to really stop basic lookups from returning your IPs, but we can only proxy web traffic & some records on your domain (mail, for example) may still return your server IP.
We do have some tips on minimizing the probability that someone could find it easily with these guidelines.
At the bottom, it's all about socket communications. If there is some way to get the ip of the both users, why can't the connection be directly setup between the users instead of having to go thru a server in the middle?
My 2 cents:
No one out there forces us to have a server based real-time communication model. Infact XMPP have an extension called "Serverless Messaging" which defines how to communicate over local or wide-area networks using the principles of zero-configuration networking for endpoint discovery and the syntax of XML streams and XMPP messaging for real-time communication. This method uses DNS-based Service Discovery and Multicast DNS to discover entities that support the protocol, including their IP addresses and preferred ports.
P2P chat applications have been for over a decade now. Having a server in the middle is purely a decision dependent upon your application needs. If your application can live with chats getting lost while the user was transitioning between online/offline status, then you can very well have a direct P2P model going. Similarly, there are a loads and loads of advantages (contact list management, avatars, entity discovery, presence authorization, offline messages, ....) when it comes to choosing a server based messaging model. If you try to have all this right inside your P2P based clients, they might die or under-perform because of all the work they will need to perform by themselves.
"WebSockets" were not designed for P2P/Serverless communication, rather they were designed to provide a standardized PUSH semantic over stateless HTTP protocol. In short, "WebSockets" is a standardized way replacing hacky comet, long-polling, chunked-encoding, jsonp, iframe-based and various other technique developers have been using to simulate server push over HTTP.
Named WebSockets (if someday it is fully and widely supported) could be the solution.
http://namedwebsockets.github.io/spec/
Named WebSockets are useful in a variety of collaborative local device
and local network scenarios: Discover matching peer services on the
local device and/or the local network.
Direct communication between users is possible in Peer To Peer (P2P) networks. In P2P each participant can act as client as well as server. But for P2P networks you need to write a separate program to make the communication possible.
Web Sockets let you leverage existing common browsers as clients. All depends on what is the purpose of your application and how you want to deploy it.
If there is some way to get the ip of the both users
You nailed the answer right in your question.
Most machines I use have IP address of 192.168.0.10 (or similar from 192.168. private network) and are deep, deep behind several layers of NAT. With the end of free IPv4 address pool and IPv6 nowhere near sight, this is the reality most users live. Having a stable intermediary of known, routable address helps a ton working around this issue.
WebSockets don't allow the socket to listen for connections, only to connect as a client to a server (not reverse). Technically they could make it allow this, but as far as I understand the spec doesn't currently (nor is it expected to) allow listen functionality for WebSockets.
The new WebRTC (http://www.webrtc.org/) spec looks like it might support peer-to-peer connections. I have not played with WebRTC at all so I'm not in a position to comment on it. I think it would be a bit more involved than WebSocket stuff. Maybe someone who knows WebRTC better can chime in. (Also apart from the latest version of Chrome I'm not sure if any of the other browsers really support WebRTC yet).
Writing an iPhone app in which I want to save the user the grief of typing in IP addresses by finding other clients on the local network.
Is this possible?
If so, what is the preferred way of doing this?
Yes, use Bonjour. See NSNetService.
This class is used to advertise information about the service you're running using multicast DNS. Use NSNetServiceBrowser to find published services of the type you're interested in.
The clients need some way to register with the server. Or you can use portknocking. Long time back there was a protocol from Novell SLP. There is a OpenSLP now. Found a interesting link, I hope this helps
http://www.opendoor.com/shareway/slp.html
I'm researching how to code an iPhone app that needs to connect to an online service to get data. The online service only provides access to specified IP addresses or ranges, so iPhones won't be able to connect directly, and the request will have to go through a server. I looked into setting up my own forward proxy server (which the service in question are happy with, by the way), which I guess would do the job for most other platforms. Unfortunately the iPhone does not seem to allow configuring a proxy address programmatically. Is there another potential solution for accessing the content from an intermediate server, that would show the online service the IP address of the server, rather than each individual iPhone?
Many thanks
Steve
It appears that using cURL is one way to achieve this. There should be bindings available for Cocoa.
I'll let people know how it goes in the comments.
Steve