Python : TCP health monitoring with socket module

Here is a TCP health monitoring script with socket module.

$ cat tcp3way.py #!/usr/bin/env python import sys import socket argvs = sys.argv argc = len(argvs) def client(host, port):    try:        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)        port = int(argvs[2])        s.connect((host, port))        #print "success"        return True    except:        #print "can't connect"        return False # close a socket    finally:        #print "close a socket"        s.close() if __name__ == "__main__":    if argc == 3:        result = client(argvs[1], argvs[2])        if result == True:            print "can connect to %s:%s" % (argvs[1], argvs[2])        else:            print "can not connect to %s:%s" % (argvs[1], argvs[2])                else:        print("usage python tcp3way.py IPaddress PORT")

$ python tcp3way.py 192.168.11.1 80 can connect to 192.168.11.1:80

Here is a capture data.

1   0.000000 192.168.11.100 -> 192.168.11.1 TCP 74 53387 > 80 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=1355687 TSecr=0 WS=128 1   2   0.999319 192.168.11.100 -> 192.168.11.1 TCP 74 [TCP Retransmission] 53387 > 80 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=1355937 TSecr=0 WS=128 2   3   1.003364 192.168.11.1 -> 192.168.11.100 TCP 74 80 > 53387 [SYN, ACK] Seq=0 Ack=1 Win=5792 Len=0 MSS=1460 SACK_PERM=1 TSval=531209006 TSecr=1355937 WS=2  4   1.003462 192.168.11.100 -> 192.168.11.1 TCP 66 53387 > 80 [ACK] Seq=1 Ack=1 Win=29312 Len=0 TSval=1355938 TSecr=531209006  5   1.003603 192.168.11.100 -> 192.168.11.1 TCP 66 53387 > 80 [FIN, ACK] Seq=1 Ack=1 Win=29312 Len=0 TSval=1355938 TSecr=531209006  6   1.005485 192.168.11.1 -> 192.168.11.100 TCP 66 80 > 53387 [ACK] Seq=1 Ack=2 Win=5792 Len=0 TSval=531209007 TSecr=1355938  7   1.183689 192.168.11.1 -> 192.168.11.100 TCP 66 80 > 53387 [FIN, ACK] Seq=1 Ack=2 Win=5792 Len=0 TSval=531209039 TSecr=1355938  8   1.183760 192.168.11.100 -> 192.168.11.1 TCP 66 53387 > 80 [ACK] Seq=2 Ack=2 Win=29312 Len=0 TSval=1355983 TSecr=531209039

$ python tcp3way.py 192.168.11.1 8080 can not connect to 192.168.11.1:8080

capture data

1   0.000000 192.168.11.100 -> 192.168.11.1 TCP 74 58051 > 8080 [SYN] Seq=0 Win=29200 Len=0 MSS=1460 SACK_PERM=1 TSval=1370632 TSecr=0 WS=128  2   0.004244 192.168.11.1 -> 192.168.11.100 TCP 54 8080 > 58051 [RST, ACK] Seq=1 Ack=1 Win=0 Len=0