Bug 34764 - TcpClient (and UdpClient) constructors leak a socket on exception
Summary: TcpClient (and UdpClient) constructors leak a socket on exception
Alias: None
Product: Class Libraries
Classification: Mono
Component: System ()
Version: master
Hardware: Other Other
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2015-10-12 12:00 UTC by Steffen Kieß
Modified: 2016-10-10 14:49 UTC (History)
2 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Steffen Kieß 2015-10-12 12:00:26 UTC
Description of Problem:
Some constructors for TcpClient can leak a socket if they throw an exception after the socket has been created. In this case the caller cannot destroy the TcpClient (because the constructor threw an exception) and the socket will remain open until it is collected by the GC.

Steps to reproduce the problem:
cat > test.cs << EOF
using System;
using System.Diagnostics;
using System.Net.Sockets;
public class Test {
  public static void Main () {
    for (int i = 0; i < 2000; i++) {
      try {
        // Assuming nothing is running on port 1234
        using (var cl = new TcpClient ("", 1234)) {
        //using (var cl = new TcpClient ()) {
        //  cl.Connect ("", 1234);
        Console.WriteLine ("Success");
      } catch (Exception e) {
        Console.WriteLine ("Error: " + e.Message);
    //Process.Start (new ProcessStartInfo ("sh", "-c 'ls -l /proc/$PPID/fd/'")).WaitForExit ();
gmcs test.cs
mono test.exe | uniq -c

Actual Results:
   1021 Error: Connection refused
    979 Error: Too many open files

Expected Results:
   2000 Error: Connection refused

Probably all TcpClient and UdpClient constructors should call Close() if the constructor fails.
Comment 1 Marek Safar 2016-10-10 14:49:03 UTC
Works as expected with Mono 4.8