[Help-glpk] Getting a public key

[???]

I have a problem installing GLPK.

I downloaded glpk-4.43.tar.gz.sig and glpk-4.43.tar.gz.
And run a command like this :
       gpg --verify glpk-4.32.tar.gz.sig

But this command failed because I didn #39;t have the required public key.
So I run the following command to import it :
        gpg --keyserver keys.gnupg.net --rec-keys 5981E818

This command also failed with below message.

gpg: requesting key 5981E818 from hkp server keys.gnupg.net
gpgkeys: HTTP fetch error 7: couldn #39;t connect to host
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

What is the problem?

Thanks,

-Mujun
I have a problem installing GLPK.

I downloaded glpk-4.43.tar.gz.sig and glpk-4.43.tar.gz.
And run a command like this :
       gpg --verify glpk-4.32.tar.gz.sig

But this command failed because I didn't have the required public key.
So I run the following command to import it :
        gpg --keyserver keys.gnupg.net --rec-keys 5981E818

This command also failed with below message.

gpg: requesting key 5981E818 from hkp server keys.gnupg.net
gpgkeys: HTTP fetch error 7: couldn't connect to host
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

What is the problem?

Thanks,

-Mujun