tools: add server query client example

tools/query.py

@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+
+# simple client for server status queries
+
+import sys, os, socket, struct, time
+
+DEFAULT_PORT = 27100
+QUERY_MAGIC = b"PDQM\x01"
+MAX_WAIT = 5.0
+
+def checksum(data):
+  chk = 1
+  for b in data[:-2]:
+    chk = (chk + b) % 65521
+  return chk
+
+def eat_string(data):
+  strlen = struct.unpack_from("<H", data)[0]
+  strdata = data[2:strlen + 2]
+  return strdata[:-1].decode(encoding='utf-8'), data[2 + strlen:]
+
+if len(sys.argv) < 2:
+  print("usage: query <address>[:<port>]")
+  sys.exit(1)
+
+addrstr = sys.argv[1].strip()
+host = addrstr
+port = None
+
+if addrstr.startswith('[') and ("]:" in addrstr):
+  # [ipv6]:port
+  host, sep, port = addrstr.rpartition(':')
+elif addrstr.count(':') == 1:
+  # possibly ipv4:port or hostname:port
+  host, sep, port = addrstr.rpartition(':')
+
+host = host.strip('[]')
+
+if port != None:
+  port = int(port)
+else:
+  port = DEFAULT_PORT
+
+sockfam = socket.AF_INET
+if ':' in host:
+  sockfam = socket.AF_INET6
+
+sock = socket.socket(sockfam, socket.SOCK_DGRAM)
+sock.settimeout(MAX_WAIT)
+
+# send query magic to server
+sock.sendto(QUERY_MAGIC, (host, port))
+
+# wait for response
+data = sock.recv(256)
+
+# check magic
+if data[:5] != QUERY_MAGIC:
+  print("invalid magic: expected", QUERY_MAGIC, "got", data[:5])
+  sys.exit(1)
+
+# check checksum
+chkremote = struct.unpack("<H", data[-2:])[0]
+chklocal = checksum(data)
+if chkremote != chklocal:
+  print("invalid checksum: expected", chklocal, "got", chkremote)
+  sys.exit(1)
+
+# check size
+datalen = struct.unpack("<H", data[5:7])[0]
+if datalen > len(data):
+  print("invalid size: expected", len(data), "got", datalen)
+  sys.exit(1)
+
+data = data[7:datalen - 2]
+
+# unpack fixed size part of the response
+msgdata = struct.unpack_from("<LBBBBB", data)
+# unpack strings from the end of the response
+hostname, data = eat_string(data[9:])
+romname, data = eat_string(data)
+moddir, data = eat_string(data)
+
+print("protocol ver:", msgdata[0])
+print("in progress:", msgdata[1])
+print("clients: {0}/{1}".format(msgdata[2], msgdata[3]))
+print("stage num:", hex(msgdata[4]))
+print("scenario:", msgdata[5])
+print("host name:", hostname)
+print("rom name:", romname)
+print("mod dir:", moddir)