java - DatagramSocket Broadcast Behavior (Windows vs. Linux) -


backstory:
have wireless device creates it's own ssid, assigns ip address using auto-ip, , begins broadcasting discovery information 255.255.255.255. (unfortunately, not easily support multicast)

what i'm trying do:
need able receive discovery information, send configuration information device. problem is, auto-ip, "ip negotiation" process can take minutes on windows, etc (during time can see broadcasts , can send broadcast information device).

so enumerate connected network interfaces (can't directly tell used talk device), create datagramsocket each of addresses, start listening. if receive discovery information via particular socket, know can use same socket send data device. this works on windows.

the problem:
on linux , osx, following code not receive broadcast packets: 

byte[] addr = {(byte)169, (byte)254, (byte)6, (byte)215};   datagramsocket foo = new datagramsocket(new inetsocketaddress(inetaddress.getbyaddress(addr), port_num));   while (true)   {   byte[] buf = new byte[256];   datagrampacket pct = new datagrampacket(buf, buf.length);   foo.receive(pct);   system.out.println( iobuffer.wrap(buf).gethexdump() );   }

in order receive broadcast packets (on linux/osx), need create datagramsocket using:
datagramsocket foo = new datagramsocket(port_num);

however, when use socket send data device, packet routed os (i'm assuming) , since interface of interest may in middle of auto-ip negotiation, fails.

thoughts on following?

  • how "working" windows behavior happen on linux/osx
  • a better way handle process

thanks in advance!

i not think problem code. have checked if osx/linux has correctly allowed address / port number through firewalls? had simple problem in past =p..

fyi, there nice technology called zero-configuration built solve problem. easy learn recommend having @ well.

good luck.


Comments

Post a Comment

Popular posts from this blog

jquery - How can I dynamically add a browser tab? -

since using iframes house external pages are, accounts "not preferred method" , disallowed sites (flickr, one), want dynamically generate browser tabs. e.g., when user submits form, want dynamically generate tab on browser in response submitted. e.g., might want add new tab url like: http://www.bigsurgarrapata.com/contact how in jquery? you want form target attribute action attribute. http://www.w3schools.com/tags/att_form_target.asp browsers have ultimate control on result of target attribute open new tab value of _blank. <form action="contact_submit.php" target="_blank" method="post">
Read more

node.js - Getting the socket id,user id pair of a logged in user(s) -

i have web application done using node js , in it,i have authentication system requires users log in before can access pages. have 2 pages,the homepage , updates page. from read docs,a new socket id issued when user opens tab in browser. me being admin,i know socket id of logged in user , more so,the socket id,logged in user id pair logged in users. what method can use socket id,logged in user id pair make sure broadcast realtime info users online?.
Read more

keyboard - C++ GetAsyncKeyState alternative -

i using windows.h library's getasynckeystate function define key pushed on keyboard . here program returns int value of pushed key example. #include <iostream> #include <windows.h> using namespace std; int main (){ char i; for(i=8;i<190;i++){ if(getasynckeystate(i)== -32767){ cout<<int (i)<<endl; } } return 0; } but trying make opengl simple game , function appeared slow . there function not need cycle 180 times , if statement . thanks you're trying make opengl game, you're going use glfw. if that's case can away using glfwgetkey() such: if (glfwgetkey(glfw_key_up) == glfw_press) {...} if (glfwgetkey(glfw_key_down) == glfw_press) {...} that method nicely explained in tutorial 6 opengl-tutorial.org . should start first tutorial of beginners tutorials , later intermediate tutorials . if you're going make win32 window can listen wm_keydown or wm_keyup messages , virtua
Read more