/sockets/sniffer.py

# Sample incoming packet sniffer
import socket, sys, struct

#reload(sys)
#sys.setdefaultencoding('utf8')

# INET, streaming socket
try:
    #s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_ICMP)
    #s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_UDP)
    s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_TCP)
    #s = socket.socket(socket.AF_PACKET, socket.SOCK_RAW, socket.ntohs(0x0003))
except socket.error, msg:
    print('Error: %s, Message: %s'%(str(msg[0]),msg[1]))
    sys.exit()

# Capture packets
while True:
    # packet string from tuple
    packet = s.recvfrom(65565)[0]
    
    # unpack ip header
    ip_header = struct.unpack('!BBHHHBBH4s4s', packet[0:20])
    version = ip_header[0] >> 4
    iph_length = (ip_header[0] & 0xF) * 4
    ttl = ip_header[5]
    protocol = ip_header[6]
    src_addr = socket.inet_ntoa(ip_header[8]);
    dest_addr = socket.inet_ntoa(ip_header[9]);
    
    print('Version: %s'%str(version))
    print('IP Header Length: %s'%str(iph_length))
    print('TTL: %s'%str(ttl))
    print('Protocol: %s'%str(protocol))
    print('Source Address: %s'%str(src_addr))
    print('Destination Address: %s'%str(dest_addr))

    # unpack tcp header
    tcp_header = struct.unpack('!HHLLBBHHH', packet[iph_length:iph_length+20])
    src_port = tcp_header[0]
    dest_port = tcp_header[1]
    seq = tcp_header[2]
    ack = tcp_header[3]
    tcph_length = tcp_header[4] >> 4
    
    print('Source Port: %s'%str(src_port))
    print('Destination Port: %s'%str(dest_port))
    print('Sequence Number: %s'%str(seq))
    print('Acknowledgement: %s'%str(ack))
    print('TCP Header Length: %s'%str(tcph_length))
    
    # get data
    header_size = iph_length + tcph_length * 4
    data_size = len(packet) - header_size
    data = packet[header_size:]
    
    print('Data: %s'%data.decode())