Eclipse help won't show under Ubuntu

Question

Whenever I open some help within eclipse I get a page saying:

Server Error. The following error occurred: [code=CANT_CONNECT_LOOPBACK] Cannot connect due to potential loopback problems

I'm running Ubuntu 10.04.

Any ideas what this can be?

UPDATE Some commands outputs (some private info replaced):

$ ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:xx:xx:xx:xx:xx  
          inet addr:123.12.123.235  Bcast:123.12.456.255  Mask:255.255.254.0
          inet6 addr: fe80::xxx:eff:xxxx:xxxx/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1343040 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1133672 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:829265876 (829.2 MB)  TX bytes:242912202 (242.9 MB)
          Memory:f3200000-f3220000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:125 errors:0 dropped:0 overruns:0 frame:0
          TX packets:125 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:15910 (15.9 KB)  TX bytes:15910 (15.9 KB)

$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
123.12.123.0    0.0.0.0         255.255.254.0   U     1      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     1000   0        0 eth0
0.0.0.0         123.12.456.254  0.0.0.0         UG    0      0        0 eth0

$ sudo netstat -anp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      765/portmap     
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      871/sshd        
tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      1181/cupsd      
tcp        0      0 0.0.0.0:52068           0.0.0.0:*               LISTEN      786/rpc.statd   
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      1186/mysqld     
tcp        0      0 0.0.0.0:53709           0.0.0.0:*               LISTEN      -               
tcp        0      0 123.12.123.235:755      123.12.5.48:2049        ESTABLISHED -               
tcp        0      0 123.12.123.235:60793    123.12.5.129:8080       ESTABLISHED 2264/firefox-bin
tcp        0      0 123.12.123.235:57940    123.12.5.43:8080        ESTABLISHED 2264/firefox-bin
tcp        0      0 123.12.123.235:57928    123.12.5.43:8080        CLOSE_WAIT  2247/google-chrome
tcp        0      0 123.12.123.235:35767    123.12.5.129:8080       ESTABLISHED 2247/google-chrome
tcp        0      0 123.12.123.235:57930    123.12.5.43:8080        ESTABLISHED 2247/google-chrome
tcp        0      0 123.12.123.235:57931    123.12.5.43:8080        CLOSE_WAIT  2247/google-chrome
tcp6       0      0 :::80                   :::*                    LISTEN      1278/apache2    
tcp6       0      0 :::22                   :::*                    LISTEN      871/sshd        
tcp6       0      0 ::1:631                 :::*                    LISTEN      1181/cupsd      
tcp6       0      0 :::55934                :::*                    LISTEN      1956/eclipse    
tcp6       0      0 :::5900                 :::*                    LISTEN      1792/vino-server
udp        0      0 0.0.0.0:35631           0.0.0.0:*                           912/avahi-daemon: r
udp        0      0 0.0.0.0:962             0.0.0.0:*                           786/rpc.statd   
udp        0      0 0.0.0.0:68              0.0.0.0:*                           1575/dhclient   
udp        0      0 0.0.0.0:46149           0.0.0.0:*                           -               
udp        0      0 0.0.0.0:5353            0.0.0.0:*                           912/avahi-daemon: r
udp        0      0 0.0.0.0:111             0.0.0.0:*                           765/portmap     
udp        0      0 0.0.0.0:36211           0.0.0.0:*                           786/rpc.statd   
udp        0      0 123.12.123.235:123      0.0.0.0:*                           1689/ntpd       
udp        0      0 127.0.0.1:123           0.0.0.0:*                           1689/ntpd       
udp        0      0 0.0.0.0:123             0.0.0.0:*                           1689/ntpd       
udp6       0      0 fe80::227:eff:fe07::123 :::*                                1689/ntpd       
udp6       0      0 ::1:123                 :::*                                1689/ntpd       
udp6       0      0 :::123                  :::*                                1689/ntpd       

Active UNIX domain sockets (servers and established) due to post size limit.

UPDATE 2 My proxy bypass settings:

Answer 1

Eclipse help is actually an HTTP server.

This is probably a permissions problem with your installation of Eclipse.

I have no suggestions except to check the permissions on your Eclipse folder, or delete and reinstall Eclipse.

Answer 2

Basically, this error means that Eclipse is failing to establish a TCP/IP connection to your localhost using 127.0.0.1 (Eclipse starts a server for the Help).

If you are using some specific proxy settings (either global at the OS level or local at the Eclipse level), double check that you are bypassing the proxy for localhost and 127.0.0.1.

If this doesn't help, try setting the hostname that help uses to localhost when starting eclipse (either on the command line or in the eclipse.ini):

eclipse -vmargs -Dserver_host=localhost

Answer 3

Hi there, had the same problem recently installing and running Eclipse on 9.10. Found that the default settings for Eclipse were fine but 9.10 had no proxy bypass set for 127.0.0.1 in its system settings. Also had to install Apache2 via Synaptic. I installed Apache2, did not change any settings for Apache2 and then went System > Preferences > Network Proxy Preferences clicked on Ignored Hosts and added "127.0.0.1". Reset the Eclipse Network Preferences back to default, restarted Eclipse and help worked perfectly. Hope this works for others.

Answer 4

David, thanks for the netstat output; you'll notice that Eclipse is listening on an IPv6 port:

Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name

tcp6 0 0 :::55934 :::* LISTEN 1956/eclipse

Is your proxy configuration set to bypass both 127.0.0.1 and ::1?

Answer 5

Make sure your /etc/hosts file is properly done. Usually

• if the line containing 127.0.0.1 has your host name remove it and just leave 'localhost'
• if the opposite were true, try adding your hostname to it :)

such things happen because gnome is trying to match hostname and sockets to handle UI things. Might be worth asking on superuser..