Check If an IP Is SSH’able

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I often need to determine if I can ssh into an IP address. In other world, for the server identified by the IP address, is the SSH port (22) is open?

First Attempt: Use bash and ssh

In my first attempt, I used the ssh command from bash to check. This approach is not doable because I don’t know in advance the user name and password; all I know is the IP address.

Second Attempt: Use the socket Library

In this attempt, I use the socket library and attempt to connect to the IP address on port 22:

import socket


def sshable(ip_address, port=22):
    """
    Returns True if the IP address is ssh'able, False otherwise
    """
    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
        return_code = sock.connect_ex((ip_address, port))
    return return_code

Sample usage:

if not sshable("192.1.1.254"):
    print("Cannot ssh into address")

In the function above, note that I used the connect_ex method instead of connect. The difference is the former returns a none-zero error code upon failure; whereas the later will throw some exception.

Conclusion

Small functions like this is intuitive to look at, and if someone spend a few minutes to look up online would come up with it. The point here is to have it ready, when the need arise, I only need to copy it and use.

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