r - How do you get a data frame that dont match in two data frames? -

i have 2 data frames:

df1

servername web01 web02 j2k101 tomcat101   prdc1001 

and df2

servername application web01      web j2k10      internal tomcat101  application 

i want use merge command merge df1 , df2 servernames have application associated them this

merge(df1,df2, by=c("servername") 

i want list of servers don't have application name. how that?

df1[!(df1$servername %in% df2$servername),] 

note, have inconsistent capitalisation. if want fixed:

df1[!(toupper(df1$servername) %in% toupper(df2$servername)),]