iphone - How to set "KEEP ALIVE" for socket connection in iOS? -

we have made chat app iphone using java chat server.

we have used socket this. on ios side have used following code ;

#import <cfnetwork/cfnetwork.h> #import <sys/socket.h> #import <sys/types.h>  - (void) viewdidload {      [self initnetworkcommunication]; }  #pragma mark network connection - (void) initnetworkcommunication {     cfreadstreamref readstream;     cfwritestreamref writestream;     cfstreamcreatepairwithsockettohost(null, (cfstringref)@"xx.xx.xx.xx", xxxx, &readstream, &writestream);      inputstream = (nsinputstream *)readstream;     outputstream = (nsoutputstream *)writestream;     [inputstream setdelegate:self];     [outputstream setdelegate:self];     [inputstream scheduleinrunloop:[nsrunloop currentrunloop] formode:nsdefaultrunloopmode];     [outputstream scheduleinrunloop:[nsrunloop currentrunloop] formode:nsdefaultrunloopmode];      [inputstream open];     [outputstream open];  } 

but whenever app goes in background , socket disconnects. so, have make socket "keep alive".

on server side , have achieved socket.setkeepalive(true, 2000); , cant able set on app (i.e ios) side.

we have searched on these links - link1 , link2

they have specified use code following make socket keep alive ;

cfdataref data = (cfdataref)cfwritestreamcopyproperty(( cfwritestreamref)outputstream, kcfstreampropertysocketnativehandle);      if(data)     {         cfsocketnativehandle socket_handle = *(cfsocketnativehandle *)cfdatagetbyteptr(data);         cfrelease(data);              nslog(@"sock handle: %x", socket_handle);              //enabling keep alive         if( setsockopt( socket_handle, sol_socket, so_keepalive, &opt, sizeof( opt ) ) < 0 )         {             nslog(@"yikes 2: failed set keepalive! errno: %s", strerror(errno));         }    } 

we have tried code not able find vales of socket_handle, sol_socket, so_keepalive, &opt, sizeof( opt ) variables.

so how to make socket connection keep alive in ios (objective-c) ?

thanks.

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> 

on .m file