pingserver: refactor for separate responsibility

refs #2793

Change-Id: I39e1794fa276d168427eac0164d481109adc6cfe
diff --git a/tools/ping/wscript b/tools/ping/wscript
index 0301eeb..575e395 100644
--- a/tools/ping/wscript
+++ b/tools/ping/wscript
@@ -12,6 +12,6 @@
     bld.program(
         features='cxx',
         target='../../bin/ndnpingserver',
-        source='ndn-ping-server.cpp',
+        source=bld.path.ant_glob('server/*.cpp'),
         use='core-objects',
         )