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curlfiddler

Why is curl trying to connect to localhost instead of going out to the internet?

I'm connected to the Internet: 

user5@system5:~$ ifconfig
enp4s0    Link encap:Ethernet  HWaddr 40:16:7e:82:55:5b  
      UP BROADCAST MULTICAST  MTU:1500  Metric:1
      RX packets:0 errors:0 dropped:0 overruns:0 frame:0
      TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
      Interrupt:19 

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:65536  Metric:1
      RX packets:5316 errors:0 dropped:0 overruns:0 frame:0
      TX packets:5316 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1 
      RX bytes:617751 (617.7 KB)  TX bytes:617751 (617.7 KB)

wlp3s0    Link encap:Ethernet  HWaddr 9c:d2:1e:61:c0:f3  
      inet addr:10.64.117.148  Bcast:10.255.255.255  Mask:255.0.0.0
      inet6 addr: fe80::c5b3:e44b:49ec:f18/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:26669 errors:0 dropped:0 overruns:0 frame:0
      TX packets:29074 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:16174458 (16.1 MB)  TX bytes:8474175 (8.4 MB)

But when running a curl command, it says unable to connect to 127.0.0.0. 

user5@system5:~$ curl -L https://packages.microsoft.com/keys/microsoft.asc | sudo apt-key add -
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0curl: (7) Failed to connect to 127.0.0.1 port 8888: Connection refused
gpg: no valid OpenPGP data found.

why is it trying to use localhost? I swear I've used curl in the past without issue.

EDIT:

Hosts file in /etc/hosts: 

127.0.0.1 localhost 
127.0.1.1 system5.

DNS settings in /etc/network/interfaces: 

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

EDIT 2:

The output of env command showed

http_proxy: 127.0.0.1

I did indeed install Fiddler the other day. I set up the proxy for Firefox, but was unaware it affected my system proxy settings as well.

To fix the curl issue I used gnome GUI: System Settings/Networking/Network Proxy/None/Apply Systemwide. Had to restart computer for changes to take effect.

Solution

  • It seems your curl is trying to connect to a proxy server instead of connecting to the internet directly.

    Check your environment by command env and see if there is any http_proxy.

    Also, check if you have some debugging tools like Fiddler or TCPDump or Charles proxy or Jmeter setup, as they may create a proxy server.

    You can also run curl with -v to get further info: curl -v -L https://packages.microsoft.com/keys/microsoft.asc