Getting several data at a time by UDP - objective-c

Question

Client (iOS) sends a message and the server checks it and answers.
iOS displays the answer.
There are two types of answer. One is just an answer. Server sends only one time.
The other is a little different. Server sends 20 times.
When server sends one time, I can process well. It's not difficult.
The problem is with the second type:
I tried two way of getting the data.
First, I used a simple CFSocket example with some modification. When it gets a message, it works well. When it gets 20 messages, it stops with an error. It says "Program received signal 'SIGABRT' "
//main code
CFSocketRef ref = CFSocketCreate(kCFAllocatorDefault, PF_INET, SOCK_DGRAM, 0, kCFSocketReadCallBack|kCFSocketDataCallBack|kCFSocketConnectCallBack|kCFSocketWriteCallBack, CFSockCallBack, NULL);
struct sockaddr_in theName;
struct hostent *hp;
theName.sin_port = htons(5003);
theName.sin_family = AF_INET;
hp = gethostbyname(IPADDRESS);
if( hp == NULL ) {
return;
}
memcpy( &theName.sin_addr.s_addr, hp->h_addr_list[PORT_NUM], hp->h_length );
CFDataRef addressData = CFDataCreate( NULL, &theName, sizeof( struct sockaddr_in ) );
CFSocketConnectToAddress(ref, addressData, 30);
CFRunLoopSourceRef FrameRunLoopSource = CFSocketCreateRunLoopSource(NULL, ref , 0);
CFRunLoopAddSource(CFRunLoopGetCurrent(), FrameRunLoopSource, kCFRunLoopCommonModes);
//Callback Method
void CFSockCallBack (
CFSocketRef s,
CFSocketCallBackType callbackType,
CFDataRef address,
const void *data,
void *info
) {
NSLog(#"callback!");
if(callbackType == kCFSocketDataCallBack) {
[lock lock];
NSLog(#"has data");
UInt8 * d = CFDataGetBytePtr((CFDataRef)data);
int len = CFDataGetLength((CFDataRef)data);
for(int i=0; i < len; i++) {
// NSLog(#"%c",*(d+i));
}
//Data processing area=
[lock unlock];
}
if(callbackType == kCFSocketReadCallBack) {
NSLog(#"to read");
char buf[100] = {0};
int sock = CFSocketGetNative(s);
NSLog(#"to read");
NSLog(#"read:%d",recv(sock, &buf, 100, 0));
NSLog(#"%s",buf);
}
if(callbackType == kCFSocketWriteCallBack) {
NSLog(#"to write");
char sendbuf[100]={0x53, 0x4D, 0x49, 0x43, 0x2};
//strcpy(sendbuf,"GET / HTTP/1.0\r\n\r\n");
//NSLog(#"%c",0x53);
CFDataRef dt = CFDataCreate(NULL, sendbuf, 5);
CFSocketSendData(s, NULL, dt, strlen(sendbuf));
}
if(callbackType == kCFSocketConnectCallBack) {
NSLog(#"connected");
}
}
The second way is using CocoaAsyncSocket. It seems to work well. But sometimes it stops with an error.
I used GCDAsyncUDPSocket. It stops randomly with signal "EXC_BAD_ACCESS".
I did it well on Android... So I think there is some other way possible.