VNC Viewer Free Edition 4.1.2 for X: "Connection reset by peer (104)"

by Jan Polnicky on Aug 19, 2009 12:00:00 AM

Today I tested OracleVM (OVM) templates on their own distribution of Oracle Enterprise Linux (OEL) 5 with seeded VNC Viewer Free Edition 4.1.2 for X. All went fine, but the VNC connection to virtual machine was not painless as I expected.

[root@oram ~]# rpm -qa "vnc|xen"
 kernel-xen-2.6.18-128.el5
 xen-3.0.3-80.el5
 kmod-gfs-xen-0.1.31-3.el5
 kmod-cmirror-xen-0.1.21-10.el5
 vnc-4.1.2-14.el5
 kmod-gnbd-xen-0.1.5-2.0.1.el5
 vnc-server-4.1.2-14.el5

On a brand new OEL5 system with virtualization support, I have created a new virtual machine with a fresh OEL4 (plain OS), and set appropriate memory for the virtual domain using the Xen management user interface commands. I also checked if the VNC port was allocated with the command virsh dumpxml:

[root@oram ~]# xm create /OVS/running_pool/OVM_EL4U6_X86_PVM_4GB/vm.cfg
 Using config file "/OVS/running_pool/OVM_EL4U6_X86_PVM_4GB/vm.cfg".
 Started domain OVM_EL4U6_X86_PVM_4GB
 [root@oram ~]# xm mem-set 1 1024
 [root@oram ~]# xm list
 Name ID Mem(MiB) VCPUs State Time(s)
 Domain-0 0 997 2 r----- 284.5
 OVM_EL4U6_X86_PVM_4GB 1 1023 1 -b---- 73.6
 [root@oram ~]# virsh dumpxml OVM_EL4U6_X86_PVM_4GB |grep port
 <graphics type='vnc' port='5900' listen='0.0.0.0'/>
 [root@oram ~]# netstat -l |grep 5900
 tcp 0 0 *:5900 *:* LISTEN

Now I expected that VNC Viewer would simply connect to the console of VM, but it displayed only the very first frame and then died after a few moments with a Connection reset by peer (104) error:

[root@oram ~]# vncviewer localhost:0
 VNC Viewer Free Edition 4.1.2 for X - built Jan 21 2009 14:35:26
 Copyright (C) 2002-2005 RealVNC Ltd.
 See https://www.realvnc.com for information on VNC.
 Fri Aug 14 15:59:24 2009
 CConn: connected to host localhost port 5900
 CConnection: Server supports RFB protocol version 3.8
 CConnection: Using RFB protocol version 3.8
 TXImage: Using default colormap and visual, PseudoColor, depth 8.
 Fri Aug 14 15:59:25 2009
 CConn: Using pixel format depth 6 (8bpp) rgb222
 CConn: Using ZRLE encoding
 Fri Aug 14 15:59:29 2009
 CConn: Throughput 20156 kbit/s - changing to hextile encoding
 CConn: Throughput 20156 kbit/s - changing to full colour
 CConn: Using pixel format depth 8 (8bpp) colour-map
 CConn: Using hextile encoding
 main: read: Connection reset by peer (104)

As I was able to see the VM console for a while, my first guess was that it would be related to the virtual system itself, so I decided to create another virtual domain to see if the problem is replicable. And yes, it was! (Well, in addition to the 104 error I got another one: Broken pipe (32), which was very likely related to domain auto-restarts, and easily traceable by xm list command showing the current VM domain ID changes.) And the solution for Connection reset by peer (104)? I noticed that VNC Viewer's default setting is auto-encoding selection, which means first use ZRLE and then switch to hextile if possible---that creates a problem here. When I set any encoding (fixed to either ZRLE or hextile), it started to work well:

[root@oram ~]# vncviewer localhost:0 PreferredEncoding=Hextile
 VNC Viewer Free Edition 4.1.2 for X - built Jan 21 2009 14:35:26
 Copyright (C) 2002-2005 RealVNC Ltd.
 See https://www.realvnc.com for information on VNC.
 Fri Aug 14 18:10:39 2009
 CConn: connected to host localhost port 5900
 CConnection: Server supports RFB protocol version 3.8
 CConnection: Using RFB protocol version 3.8
 TXImage: Using default colormap and visual, PseudoColor, depth 8.
 Fri Aug 14 18:10:40 2009
 CConn: Using pixel format depth 6 (8bpp) rgb222
 CConn: Using hextile encoding

VNC Viewer Free Edition 4.1.2 for X: "Connection reset by peer (104)"

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