The data sent back from the server consists of three parts: the status line, the headers and the body, for example here I'm accessing the body.
library(httr)
query3 <- "http://isc.sans.edu/api/port/80"
response <- GET(url=query3)
content(response, "text")
#> [1] "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<port>\n<number>80</number><data><date>2019-01-11</date><records>6152</records><targets>1523</targets><sources>1438</sources><tcp>96</tcp><udp>1</udp><datein>2019-01-11</datein><portin>80</portin></data><services><udp><service>www</service><name>World Wide Web HTTP</name></udp><tcp><service>www</service><name>World Wide Web HTTP</name></tcp></services>\n</port>"