UDP packet does not arrive - networking

Question

I'm not sure if this is the right place to ask this question. If not, i will remove it...
Anyway, i have made driver for enc28j60 for LPC1788 and I'm trying to send UDP message to it from iOS. Sending fails.
Communication starts by iOS sending the ARP request. On LPC i make response and send it to iOS MAC address. I have read RFC for ARP and created packet by the specification, but for some reason i dont see the response in network sniffer.
That would for sure indicate that my response routine does not work, if there was not this case when i send udp message from OSX (nc -u xxx.xxx.xxx.xxx port) that comes correctly to LPC.
The difference that i observed is that OSX sends the request which is 42bytes long and gets 60bytes long response with last 18bytes of 0's (padding bytes), and iOS sends the 60byte long request with last 4bytes as 90 eb 58 96.
I tried to respond with all padding zeros, and with copying those 4 bytes, but neither approach worked.
OSX ARP(req, res) and UDP package is visible in sniffer.
iOS ARP req is visible in sniffer and nothing else.
Any idea ?
EDIT:
IOS code:
CFSocketRef sock = CFSocketCreate(kCFAllocatorDefault, PF_INET, SOCK_DGRAM, IPPROTO_UDP, 0, NULL, NULL);
if ( sock == NULL) {
NSLog(#"CfSocketCreate Failed");
}else{
struct sockaddr_in remoteAddress;
memset(&remoteAddress, 0, sizeof(remoteAddress));
remoteAddress.sin_family = AF_INET;
remoteAddress.sin_len = sizeof(remoteAddress);
remoteAddress.sin_port = htons(1200);
remoteAddress.sin_addr.s_addr = inet_addr("192.168.5.8");
char data[] = "test";
NSData *message_data = [NSData dataWithBytes:&data length:4];
NSData* remoteAddressData = [NSData dataWithBytes:&remoteAddress length:sizeof(remoteAddress)];
CFSocketError er = CFSocketSendData(sock, (__bridge CFDataRef)(remoteAddressData), (__bridge CFDataRef)message_data, 0);
}
LPC code:
void make_arp_response (uint8_t *buffer)
{
uint16_t pos = sizeof (ethernet.source)+sizeof (ethernet.dest);
uint8_t type[2];
type[0] = ARP_TYPE>>8;
type[1] = (uint8_t)ARP_TYPE;
memcpy (buffer+pos, &type, sizeof (ethernet.type)); pos = sizeof(ethernet); //set ethernet type
arp.hwType = ((0x01)<<8);
memcpy (buffer+pos, &arp.hwType, sizeof (arp.hwType)); pos += sizeof(arp.hwType);
arp.protocol[0] = 0x08;
arp.protocol[1] = 0x00;
memcpy (buffer+pos, &arp.protocol, sizeof (arp.protocol)); pos += sizeof(arp.protocol);
memcpy (buffer+pos, &arp.macLen, sizeof (arp.macLen)); pos += sizeof(arp.macLen);
memcpy (buffer+pos, &arp.ipLen, sizeof (arp.ipLen)); pos += sizeof(arp.ipLen);
arp.opCode = (0x02) << 8;
memcpy (buffer+pos, &arp.opCode, sizeof (arp.opCode)); pos += sizeof(arp.opCode);
memcpy (buffer+pos, &macaddr, sizeof (arp.sourceMac)); pos += sizeof(arp.sourceMac);
memcpy (buffer+pos, &arp.destIP, sizeof (arp.sourceIp)); pos += sizeof(arp.sourceIp);
memcpy (buffer+pos, &arp.sourceMac, sizeof (arp.destMac)); pos += sizeof(arp.destMac);
memcpy (buffer+pos, &arp.sourceIp, sizeof (arp.destIP));
enc28j60_PacketSend(sizeof (ethernet)+sizeof (arp),buf);
}
UPDATE:
It seems that this is not just an iOS problem, but problem with Wifi clients. I have tried to send UDP from windows laptop over wifi and it also sends the ARP request but response and UDP packet got lost somehow. It seems that my ruter have some problems with my LPC :)
I have also tried to connect Arduino to the same enc28j60 board instead of LPC, and UDP communication works.
Library for arduino is found somewhere on the NET. ARP response in arduino code looks the same to me.
UPDATE 2:
Arp request:
ff ff ff ff ff ff 85 29 fb 0d c2 71 08 06 00 01
08 00 06 04 00 01 85 29 fb 0d c2 71 c0 a8 05 28
00 00 00 00 00 00 c0 a8 05 08 00 00 00 00 00 00
00 00 00 00 00 00 00 00 25 a9 c3
Arp response:
85 29 fb 0d c2 71 7b c3 53 a6 9c 55 08 06 00 01
08 00 06 04 00 02 7b c3 53 a6 9c 55 c0 a8 05 08
85 29 fb 0d c2 71 c0 a8 05 28
This response is dumped from LPC just after sending it on wire. I didnt saw it in sniffer.