some boxes on 10.x.x.x/8 would crash

.vscode/launch.json

@@ -15,7 +15,7 @@
                 "-a",
                 "ed:wark",
                 "-v",
-                "/home/ed/inc:inc:r:aed"
+                "srv::r:aed"
             ]
         },
         {

copyparty/httpconn.py

@@ -2,9 +2,24 @@
 from __future__ import print_function, unicode_literals
 
 import os
+import sys
 import ssl
 import socket
-import jinja2
+
+try:
+    import jinja2
+except ImportError:
+    print(
+        """\033[1;31m
+  you do not have jinja2 installed,\033[33m
+  choose one of these:\033[0m
+   * apt install python-jinja2
+   * python3 -m pip install --user jinja2
+   * (try another python version, if you have one)
+   * (try copyparty.sfx instead)
+"""
+    )
+    sys.exit(1)
 
 from .__init__ import E
 from .util import Unrecv

copyparty/tcpsrv.py

@@ -92,11 +92,23 @@ class TcpSrv(object):
 
         default_route = None
         s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        for ip in [
+            "10.255.255.255",
+            "172.31.255.255",
+            "192.168.255.255",
+            "239.255.255.255",
+            # could add 1.1.1.1 as a final fallback
+            # but external connections is kinshi
+        ]:
             try:
-            s.connect(("10.255.255.255", 1))
+                s.connect((ip, 1))
+                # raise OSError(13, "a")
                 default_route = s.getsockname()[0]
+                break
             except (OSError, socket.error) as ex:
-            if ex.errno not in [101, 10065]:
+                if ex.errno == 13:
+                    self.log("tcpsrv", "eaccess {} (trying next)".format(ip))
+                elif ex.errno not in [101, 10065]:
                     raise
 
         s.close()