add check if port is in use to webservexecutor

src/attackmate/executors/http/webservexecutor.py

@@ -3,14 +3,14 @@
 ============================================
 Serves files via HTTP
 """
-
+import magic
+import socket
 from attackmate.executors.baseexecutor import BaseExecutor
 from attackmate.result import Result
 from attackmate.execexception import ExecException
 from attackmate.schemas.http import WebServCommand
 from attackmate.executors.features.cmdvars import CmdVars
 from http.server import HTTPServer, BaseHTTPRequestHandler
-import magic
 from attackmate.executors.executor_factory import executor_factory
 
 
@@ -57,8 +57,27 @@ class WebServExecutor(BaseExecutor):
     def log_command(self, command: WebServCommand):
         self.logger.info(f'Serving {command.local_path} via HTTP on Port {command.port}')
 
+    def _port_in_use(self, address: str, port: int) -> bool:
+        # IPv4 and TCP
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+            # bind to the port even if it's still in TIME_WAIT
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            try:
+                # bind to the port to see if it can be used
+                s.bind((address, port))
+                return False
+            except OSError:
+                return True
+
     async def _exec_cmd(self, command: WebServCommand) -> Result:
-        address = (command.address, CmdVars.variable_to_int('Port', command.port))
+        port = CmdVars.variable_to_int('Port', command.port)
+        address = (command.address, port)
+
+        if self._port_in_use(command.address, port):
+            raise ExecException(
+                f'Cannot start webserv: port {port} on {command.address} is already in use'
+            )
+
         try:
             server = WebServe(address, WebRequestHandler, local_path=command.local_path)
             if command.keep_serving: