Hi In this #define TO16(x) ((((x) >> 8) & 0x00FF) | (((x) << 8) & 0xFF00)) sockid = socket(AF_INET, SOCK_PACKET, TO16(ETH_P_ALL)) what does SOCK_PACKET mean. In went through W.R Stevens, but I am unable to find SOCK_PACKET type. Similarly I am not able to understand what is ETH_P_ALL and the necessity of the bit operations on it. Any help will be appreciated. Thanks in advance Devan