Import and usage of different package files in protobuf?

If the package name is same then you can omit the package name from the field declaration but otherwise there is no other way. if you can include muthu.test in the same package by specifying “package muthu.other” then it is allowed.

From Google documentation of protobuf:

You can add an optional package specifier to a .proto file to prevent name clashes between protocol message types.

package foo.bar;
message Open { ... }

You can then use the package specifier when defining fields of your message type:

message Foo {
  ...
  required foo.bar.Open open = 1;
  ...
}