I have tried using GCDAsyncUdpPacket.m and .h files for creating a udp communication channel. But through that i could send only one line messages. I need to send an entire file for example an Image.
Any help would be much appreciated as I am totally new to this platform.
Since UDP is not an error checked protocol, just cramming the binary data down a UDP socket will not be reliable, as some of the packets will likely be dropped, or arrive out of order at the far end.
If you want to ensure error-checked, in-order, and reliable data, open a TCP socket and send it that way.
In IOS, you can use the NSStream class to do this, though you'll have to look at a lot of sample code to understand the various ways it can be used in an iPhone app. To implement it well, you need to understand how run-loops work (NSRunLoop) and how delegation works in Cocoa.
For me, I tend to avoid all this and start network tasks on a separate NSThread, opening a TCP socket using unix's socket(), connect() and send() primitives. Once you get these working, they can be cut and pasted into other code (or put into a personal code library) so you don't have to remember how to do it. :-)
There is a lot of sample code out there for the BSD primitives socket(), accept(), bind(), connect(), send(), and recv().
Related
I'm trying to spec out the foundations for a server application who's purpose will be to..
1 'receive' tcp and/or udp packets
2 interpret the contents (i.e. header values)
To add more detail, this server will receive 'sip invites' and respond with a '302 redirect'.
I have experience with Net::Pcap and perl, and know I could achieve this by looping for filtered packets, decoding and then using something like Net::SIP to respond.
However, there's a lot of bloat in both of these modules/applications I don't need. The server will be under heavy load, and if I run TCPDUMP on it's own, it loses packets in the kernel due to server load, so worry it wont be appropriate :(
Should I be able to achieve the same thing by 'listening' on a socket (using IO::Socket for example) and decoding a packet?
Unfortunatly by debugging, it's hard to tell if IO::Socket will give me the opportunity to see a raw packet? And instead it automatically decodes the message to a readable format!
tl;dr: I want to capture lots of SIP Invites, analyse the head values, and respond with a SIP 302 redirect. Is there a better way than using tcpdump (via Net::Pcap) to achieve this?
Thanks,
Moose
Is there a better way than using tcpdump (via Net::Pcap) to achieve this?
Yes. Using libpcap (that's what you meant instead of tcpdump in that question) is a bad way to implement a TCP-based service, as you will have to reimplement much of TCP yourself (libpcap gives you raw network-layer packets), and the packets your program gets will also get delivered to the Internet protocol stack on your machine, so:
if there's nothing on your machine listening on the TCP port to which the other machines are trying to connect, the connection requests will get a RST from the TCP code and think the connection attempt failed;
if there is something on your machine listening on that port, it'll probably accept the connection, and it and your program will both try to communicate with the other machine, which will probably confuse its TCP stack and cause various bad and random things to happen.
It's not much better for UDP:
if there's nothing on your machine listening on the UDP port to which the other machines are trying to connect, the connection requests will probably get an ICMP Port Unreachable message from the UDP code, which may make it think the connection attempt failed;
if there is something on your machine listening on that port, it'll probably accept the connection, and it and your program will both try to communicate with the other machine, which will probably confuse its SIP stack and cause various bad and random things to happen.
IO:Socket will probably not give you raw packets, and that's a good thing; you won't have to implement your own IP and TCP/UDP stack. If your goal is to implement a redirect server on your machine, you have no need to receive raw packets; you want to receive SIP INVITEs with all the lower-level processing done for you by your machine's IP/TCP/UDP stack.
If you already have a SIP implementation on your machine, and you want to act as a "firewall" for it, so that, for some INVITEs, you send back a 302 redirect and prevent the SIP implementation on your machine from ever seeing the INVITEs in question, you will need to use the same mechanism that your particular OS uses to implement firewalls. There is no libpcap-like wrapper for those mechanisms, as far as I know.
I need to listen to a TCP port and collect the binary data from the port in my iphone how this could be done . I had searched a lot for the same but did not find anything worth, please help me any links, or sample code be greatly appretiated
The only thing you need to do is open a socket, you have two options:
Create the socket in pure C:
Sockets in C
Or use the classes that Apple provides to work with sockets:
Introduction to Stream Programming Guide for Cocoa
If you are going to do something simple, the first option is the easiest
There is a very useful socket library called GCDAsyncSocket on github that can be used to make both TCP/UDP sockets and comes with delegate methods for reading and writing data
GCDAsyncSocket
I've spent a few days looking for different solutions, but the whole area is quite complicated, and I'm wondering if anybody knows of any project where I can simply transfer NSData or an NSString or some other simple file over wifi to another iPhone on the network?
Np. Use bonjour to search for devices. Then use CocoaAsyncSocket to send and receive data. It works like a charm.
Little info about AsyncSock:
GCDAsyncSocket and AsyncSocket are TCP/IP socket networking libraries.
Here are the key features available in both:
Native objective-c, fully self-contained in one class. No need to muck
around with sockets or streams. This class handles everything for you.
Full delegate support Errors, connections, read completions, write
completions, progress, and disconnections all result in a call to your
delegate method.
Queued non-blocking reads and writes, with optional timeouts. You tell
it what to read or write, and it handles everything for you. Queueing,
buffering, and searching for termination sequences within the stream -
all handled for you automatically.
Automatic socket acceptance. Spin up a server socket, tell it to
accept connections, and it will call you with new instances of itself
for each connection.
Support for TCP streams over IPv4 and IPv6. Automatically connect to
IPv4 or IPv6 hosts. Automatically accept incoming connections over
both IPv4 and IPv6 with a single instance of this class. No more
worrying about multiple sockets.
Support for TLS / SSL Secure your socket with ease using just a single
method call. Available for both client and server sockets.
In a nutshell, I am trying to write a C++ XPCOM component which listens on a UDP port and calls a callback function (a javascript function) every time a UDP packet arrives.
Sorry if the answer is too obvious but I was wondering what are the ways to listen on a UDP port with Mozilla (Preferably something easy to do)?
I know that there is an interface called nsIServerSocket which allows some listeners to be attached to it, but this is only for opening TCP ports. Is there any UDP equivalent of this (where I can attach a listener which is notified every time a UDP packet arrives)?
I also know that I could probably use PR_OpenUDPSocket and such. Is there a way of using this without dealing with threads? (As far as I understand I have to return to the calling javascript function after opening the port).
Thanks.
Why do you need to restrict yourself to Mozilla's API if you are writing C++ code? You can use the POSIX socket API directly, see How to set up a Winsock UDP socket? for a WinSock example (the only difference for Linux and OS X should be that WSAStartup() call is unnecessary). nsIServerSocket is mainly useful for JavaScript code that doesn't have the option to use the system libraries directly.
If you prefer a straight answer to your question: no, there is no XPCOM API to create UDP sockets. You already found the NSPR API (PR_OpenUDPSocket()) but it is probably designed with DNS communication in mind since that's pretty much the only UDP communication a browser would do. Don't expect much here.
And a side-note: you might want to avoid binary XPCOM components and create a native library that can be called via js-ctypes instead. See here for the details.
So Im trying to further my understanding of sockets, but I want to start out at the lowest level first (well in C, not assembly lol)
However most sites that I deal with use the SOCK_STREAM or SOCK_DGRAM. However I have read around on Beejs guide....but I don't know if that actually deals with RAW sockets or not.
I'll obviously need to call SOCK_RAW in my call to sockets, but theirs not really a WHOLE lot of information about it. And this is just for learning purposes, i always try to understand the root of whats going on in abstraction.
Thanks
Assuming you're using Linux, I would look at the man pages for socket and packet as a start. From here and after reading a few other man pages to figure out how to actually send packets on the wire, I'd install Wireshark and experiment with sending hand-crafted packets and using Wireshark to capture and analyze them. You can learn a lot about the different network layers this way and how you can tweak different values in various headers.