minor fixes

fgex-lib/firegex/cli.py

@@ -3,10 +3,13 @@
 
 import typer
 from rich import print
+from rich.markup import escape
 from typer import Exit
 from firegex import __version__
 from firegex.nfproxy.proxysim import run_proxy_simulation
 from firegex.nfproxy.models import Protocols
+import os
+import socket
 
 app = typer.Typer(
     no_args_is_help=True,
@@ -18,6 +21,19 @@ def close_cli(code:int=1):
 
 DEV_MODE = __version__ == "0.0.0"
 
+def test_connection(host, port, use_ipv6=False):
+    family = socket.AF_INET6 if use_ipv6 else socket.AF_INET
+    sock = socket.socket(family, socket.SOCK_STREAM)
+    
+    try:
+        sock.settimeout(3)
+        sock.connect((host, port))
+        return True
+    except Exception:
+        return False
+    finally:
+        sock.close()
+
 @app.command(help="Run an nfproxy simulation")
 def nfproxy(
     filter_file: str = typer.Argument(..., help="The path to the filter file"),
@@ -31,7 +47,12 @@ def nfproxy(
 ):
     if from_address is None:
         from_address = "::1" if ipv6 else "127.0.0.1"
-        
+    if not os.path.isfile(filter_file):
+        print(f"[bold red]'{escape(os.path.abspath(filter_file))}' not found[/]")
+        close_cli()
+    if not test_connection(address, port, ipv6):
+        print(f"[bold red]Can't connect to {escape(address)}:{port}[/]")
+        close_cli()
     run_proxy_simulation(filter_file, proto.value, address, port, from_address, from_port, ipv6)
 
 def version_callback(verison: bool):