New submission from Seán Kelleher:
I have a Go server that listens to a port, runs a Python client to connect to
the port as a subcommand, and reads from the client. However, the client (as
follows) will occasionally run to completion without connecting to the port,
but without raising an exception:
import socket
import sys
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
[addr, port] = sys.argv[1].split(':')
sock.connect((addr, int(port)))
try:
sock.send("hello")
finally:
sock.close()
print "done."
`server.go` follows:
package main
import (
"log"
"net"
"os"
"os/exec"
)
func main() {
ln, err := net.ListenTCP("tcp4", &net.TCPAddr{IP: net.IPv4(127,
0, 0, 1)})
if err != nil {
log.Fatalf("%v", err)
}
defer ln.Close()
cmd := exec.Command(
"python",
"client.py",
ln.Addr().(*net.TCPAddr).String(),
)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
if err := cmd.Start(); err != nil {
log.Fatalf("%v", err)
}
defer cmd.Process.Kill()
go func() {
log.Printf("command exited with: %v", cmd.Wait())
log.Printf("closing listener: %v", ln.Close())
}()
conn, err := ln.Accept()
if err != nil {
log.Fatalf("%v", err)
}
buf := make([]byte, 1024)
n, err := conn.Read(buf)
log.Println(string(buf[:n]))
}
When the connection is successful, the output is as expected:
done.
2015/08/01 21:03:50 hello
A failed connection, by contrast, gives no indication from Python that the
command failed (`done.` is output), but it is evident that the connection was
not established:
done.
2015/08/01 20:56:55 command exited with: <nil>
2015/08/01 20:56:55 closing listener: <nil>
2015/08/01 20:56:55 accept tcp4 127.0.0.1:42550: use of closed network
connection
exit status 1
>From this, it appears as though the Python client thinks it has established a
>connection, because neither the `connect` nor the `send` call raise an
>exception.
This behaviour is corrected in Python 3 (all runs look like the first
instance), so it appears to be local to Python 2.7.
----------
components: Library (Lib)
messages: 247826
nosy: Seán Kelleher
priority: normal
severity: normal
status: open
title: Python client failing to connect to server but completing as if
successful
type: behavior
versions: Python 2.7
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue24775>
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