test: infamy: Generalize netconf_syn() to test for any TCP service

Being able to check for a TCP based service is generally useful, not
only for NETCONF. Therefore, break it out to a separate function that
allows any port to be queried.

test/infamy/netconf.py

@@ -17,18 +17,14 @@ import netconf_client.connect
 import netconf_client.ncclient
 from infamy.transport import Transport,infer_put_dict
 from netconf_client.error import RpcError
-from . import env
+from . import env, netutil
 
 
 def netconf_syn(addr):
-    try:
-        ai = socket.getaddrinfo(addr, 830, 0, 0, socket.SOL_TCP)
-        sock = socket.socket(ai[0][0], ai[0][1], 0)
-        sock.connect(ai[0][4])
-        sock.close()
+    if netutil.tcp_port_is_open(addr, 830):
         print(f"{addr} answers to TCP connections on port 830 (NETCONF)")
         return True
-    except Exception:
+    else:
         return False
 
 

test/infamy/netutil.py

@@ -0,0 +1,11 @@
+import socket
+
+def tcp_port_is_open(host, port):
+    try:
+        ai = socket.getaddrinfo(host, port, 0, 0, socket.SOL_TCP)
+        sock = socket.socket(ai[0][0], ai[0][1], 0)
+        sock.connect(ai[0][4])
+        sock.close()
+        return True
+    except Exception:
+        return False