cleanup: Make pylint and mypy happy with bootstrap_node_info.py.

other/fun/bootstrap_node_info.py

@@ -20,15 +20,16 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 """
-
-from socket import *
+import socket
 import sys
 
 if sys.version_info[0] == 2:
     print("This script requires Python 3+ in order to run.")
     sys.exit(1)
 
-def printHelp():
+
+def print_help() -> None:
+    """Print program usage to stdout."""
     print("Usage: " + sys.argv[0] + " <ipv4|ipv6> <ip/hostname> <port>")
     print("  Example: " + sys.argv[0] + " ipv4 192.210.149.121 33445")
     print("  Example: " + sys.argv[0] + " ipv4 23.226.230.47 33445")
@@ -42,57 +43,79 @@ def printHelp():
     print("  2 - didn't receive any reply from a node")
     print("  3 - received a malformed/unexpected reply")
 
-if len(sys.argv) != 4:
-    printHelp()
-    sys.exit(1)
 
-protocol = sys.argv[1]
-ip = sys.argv[2]
-port = int(sys.argv[3])
-
-INFO_PACKET_ID = b"\xF0"         # https://github.com/irungentoo/toxcore/blob/4940c4c62b6014d1f0586aa6aca7bf6e4ecfcf29/toxcore/network.h#L128
-INFO_REQUEST_PACKET_LENGTH = 78  # https://github.com/irungentoo/toxcore/blob/881b2d900d1998981fb6b9938ec66012d049635f/other/bootstrap_node_packets.c#L28
-# first byte is INFO_REQUEST_ID, other bytes don't matter as long as reqest's length matches INFO_REQUEST_LENGTH
-INFO_REQUEST_PACKET = INFO_PACKET_ID + ( b"0" * (INFO_REQUEST_PACKET_LENGTH - len(INFO_PACKET_ID)) )
+# https://github.com/irungentoo/toxcore/blob/4940c4c62b6014d1f0586aa6aca7bf6e4ecfcf29/toxcore/network.h#L128
+INFO_PACKET_ID = b"\xF0"
+# https://github.com/irungentoo/toxcore/blob/881b2d900d1998981fb6b9938ec66012d049635f/other/bootstrap_node_packets.c#L28
+INFO_REQUEST_PACKET_LENGTH = 78
+# first byte is INFO_REQUEST_ID, other bytes don't matter as long as reqest's
+# length matches INFO_REQUEST_LENGTH
+INFO_REQUEST_PACKET = INFO_PACKET_ID + (
+    b"0" * (INFO_REQUEST_PACKET_LENGTH - len(INFO_PACKET_ID)))
 
 PACKET_ID_LENGTH = len(INFO_PACKET_ID)
-VERSION_LENGTH = 4    # https://github.com/irungentoo/toxcore/blob/881b2d900d1998981fb6b9938ec66012d049635f/other/bootstrap_node_packets.c#L44
-MAX_MOTD_LENGTH = 256 # https://github.com/irungentoo/toxcore/blob/881b2d900d1998981fb6b9938ec66012d049635f/other/bootstrap_node_packets.c#L26
+# https://github.com/irungentoo/toxcore/blob/881b2d900d1998981fb6b9938ec66012d049635f/other/bootstrap_node_packets.c#L44
+VERSION_LENGTH = 4
+# https://github.com/irungentoo/toxcore/blob/881b2d900d1998981fb6b9938ec66012d049635f/other/bootstrap_node_packets.c#L26
+MAX_MOTD_LENGTH = 256
 
 MAX_INFO_RESPONSE_PACKET_LENGTH = PACKET_ID_LENGTH + VERSION_LENGTH + MAX_MOTD_LENGTH
 
 SOCK_TIMEOUT_SECONDS = 1.0
 
-sock = None
 
-if protocol == "ipv4":
-    sock = socket(AF_INET, SOCK_DGRAM)
-elif protocol == "ipv6":
-    sock = socket(AF_INET6, SOCK_DGRAM)
-else:
-    print("Invalid first argument")
-    printHelp()
-    sys.exit(1)
+def main(protocol: str, host: str, port: int) -> None:
+    """Call the bootstrap node info RPC and output the response."""
+    if protocol == "ipv4":
+        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    elif protocol == "ipv6":
+        sock = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
+    else:
+        print("Invalid first argument")
+        print_help()
+        sys.exit(1)
 
-sock.sendto(INFO_REQUEST_PACKET, (ip, port))
+    sock.sendto(INFO_REQUEST_PACKET, (host, port))
 
-sock.settimeout(SOCK_TIMEOUT_SECONDS)
+    sock.settimeout(SOCK_TIMEOUT_SECONDS)
 
-try:
-   data, addr = sock.recvfrom(MAX_INFO_RESPONSE_PACKET_LENGTH)
-except timeout:
-   print("The DHT bootstrap node didn't reply in " + str(SOCK_TIMEOUT_SECONDS) + " sec.")
-   print("The likely reason for that is that the DHT bootstrap node is either offline or has no info set.")
-   sys.exit(2)
+    try:
+        data, _ = sock.recvfrom(MAX_INFO_RESPONSE_PACKET_LENGTH)
+    except socket.timeout:
+        print("The DHT bootstrap node didn't reply in " +
+              str(SOCK_TIMEOUT_SECONDS) + " sec.")
+        print("The likely reason for that is that the DHT bootstrap node "
+              "is either offline or has no info set.")
+        sys.exit(2)
 
-packetId = data[:PACKET_ID_LENGTH]
-if packetId != INFO_PACKET_ID:
-    print("Bad response, first byte should be", INFO_PACKET_ID, "but got", packetId, "(", data, ")")
-    print("Are you sure that you are pointing the script at a Tox DHT bootstrap node and that the script is up to date?")
-    sys.exit(3)
+    packet_id = data[:PACKET_ID_LENGTH]
+    if packet_id != INFO_PACKET_ID:
+        print("Bad response, first byte should be {info_packet_id!r}"
+              " but got {packet_id!r}({data!r})".format(
+                  info_packet_id=INFO_PACKET_ID,
+                  packet_id=packet_id,
+                  data=data,
+              ))
+        print("Are you sure that you are pointing the script at a Tox "
+              "DHT bootstrap node and that the script is up to date?")
+        sys.exit(3)
 
-version = int.from_bytes(data[PACKET_ID_LENGTH:PACKET_ID_LENGTH + VERSION_LENGTH], byteorder='big')
-motd = data[PACKET_ID_LENGTH + VERSION_LENGTH:].decode("utf-8")
-print("Version: " + str(version))
-print("MOTD:    " + motd)
-sys.exit(0)
+    version = int.from_bytes(data[PACKET_ID_LENGTH:PACKET_ID_LENGTH +
+                                  VERSION_LENGTH],
+                             byteorder="big")
+    motd = data[PACKET_ID_LENGTH + VERSION_LENGTH:].decode("utf-8")
+    print("Version: " + str(version))
+    print("MOTD:    " + motd)
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 4:
+        print_help()
+        sys.exit(1)
+
+    main(
+        protocol=sys.argv[1],
+        host=sys.argv[2],
+        port=int(sys.argv[3]),
+    )