1. Is the server command service soap method available only on the local host?2. i want camera password changing in milestone management console. Is there a server command service to do the job I just mentioned?

No.

There might be firewall or similar. Also consider that you must login (I wonder if you on local could be current user).

Login see - http://doc.developer.milestonesys.com/html/index.html?base=samples/logindotnetsoap.html&tree=tree_3.html

You cannot change password on Server Command but you can on Configuration API

http://doc.developer.milestonesys.com/html/index.html?base=gettingstarted/intro_configurationapi.html&tree=tree_4.html

Also see - http://doc.developer.milestonesys.com/html/index.html?base=gettingstarted/intro_soap_protocols.html&tree=tree_4.html