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Fix code scanning alert: bind socket to 127.0.0.1 instead of all interfaces #40

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Fix code scanning alert: bind socket to 127.0.0.1 instead of all interfaces #40

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b738210
Potential fix for code scanning alert no. 2: Binding a socket to all …
tschm Jun 25, 2026
6af3b2d
Fix Windows test: occupy port on 127.0.0.1 to match find_free_port
tschm Jun 25, 2026
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4 changes: 2 additions & 2 deletions src/pycharting/core/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ def find_free_port(start_port: int | None = None, end_port: int | None = None) -
if start_port is None:
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(("", 0))
s.bind(("127.0.0.1", 0))
return s.getsockname()[1]
Comment on lines 78 to 82

if end_port is None:
Expand All @@ -87,7 +87,7 @@ def find_free_port(start_port: int | None = None, end_port: int | None = None) -
for port in range(start_port, end_port):
try:
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind(("", port))
s.bind(("127.0.0.1", port))
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
return port
Comment on lines 89 to 92
except OSError:
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4 changes: 2 additions & 2 deletions tests/test_server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -41,11 +41,11 @@ def test_raises_on_no_free_port(self):
"""Test that RuntimeError is raised when no port is free."""
import socket

# Bind on the same interface find_free_port scans ("" / all interfaces).
# Bind on the same interface find_free_port scans ("127.0.0.1").
# On Windows, 127.0.0.1:port does not conflict with 0.0.0.0:port, so the
# occupied port must be claimed on the same address to be seen as taken.
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind(("", 0))
s.bind(("127.0.0.1", 0))
occupied_port = s.getsockname()[1]
with pytest.raises(RuntimeError, match="No free port found"):
find_free_port(occupied_port, occupied_port + 1)
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