udp-holepunch - Python script for UDP holepunching using a webserver. With an example of SSH using this and sctp-echo. git clone https://benconnors.ca/git-repos/udp-holepunch

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commit 6778edcce27c74631f2d48a100a7fc34be1130fb
parent ddc495b53a04f3e41be1668be2f1e8fd093ef71e
Author: Ben Connors <benconnors@outlook.com>
Date:   Wed,  9 Sep 2026 12:11:16 -0400

Add timeout to holepunch loop

Diffstat:
M
udp_holepunch.py
 | 
15
++++++++++++---

1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/udp_holepunch.py b/udp_holepunch.py
@@ -61,7 +61,7 @@ def ssh_verify(message, signature, allowed_keys, namespace="udp-holepunch"):
 
     return True
 
-def udp_holepunch_loop(sock, other_addr, no_ack=False):
+def udp_holepunch_loop(sock, other_addr, no_ack=False, timeout=60):
     """Finalize the UDP holepunching.
 
     The general idea here is to blast them with "hello!" packets; once they receive one from us,
@@ -74,12 +74,18 @@ def udp_holepunch_loop(sock, other_addr, no_ack=False):
             sock.sendto(b"hello!", other_addr)
     else: 
         found = False
+
+        start = time.monotonic()
+        sock.settimeout(0.5)
         while True:
             sock.sendto(b"hello!" if not found else b"done!", other_addr)
 
             try:
                 resp = sock.recvfrom(100)
             except TimeoutError:
+                if time.monotonic() - start > timeout:
+                    return False
+
                 continue
 
             if resp[1] != other_addr:
@@ -101,7 +107,9 @@ def udp_holepunch_loop(sock, other_addr, no_ack=False):
             except TimeoutError:
                 break
 
-def udp_holepunch_server(local_port, server_port, server_path, no_ack=False, allowed_keys=None):
+    return True
+
+def udp_holepunch_server(local_port, server_port, server_path, no_ack=False, allowed_keys=None, timeout=60):
     """Serve as the UDP holepunching "server".
 
     Poll the given `server_path`; if a message is found from `udp_holepunch_client`, begin the
@@ -153,7 +161,8 @@ def udp_holepunch_server(local_port, server_port, server_path, no_ack=False, all
     ## Send to the client directly
     other_addr = (other_ip, other_port)
 
-    udp_holepunch_loop(c, other_addr, no_ack=no_ack)
+    if not udp_holepunch_loop(c, other_addr, no_ack=no_ack, timeout=timeout):
+        raise Exception("Holepunching timeout")
 
     c.close()