Specify connection: keep-alive in exercise 1-6

book/http.md

@@ -984,12 +984,14 @@ print the entire HTML file as if it was text. You'll want to have also
 implemented Exercise 1-4.
 
 1-6 *Keep-alive*. Implement Exercise 1-1; however, do not send
-the `Connection: close` header. Instead, when reading the body from
-the socket, only read as many bytes as given in the `Content-Length`
-header and don't close the socket afterward. Instead, save the
-socket, and if another request is made to the same server reuse the
-same socket instead of creating a new one. This will speed up repeated
-requests to the same server, which are common.
+the `Connection: close` header (send `Connection: keep-alive` instead).
+When reading the body from the socket, only read as many bytes as given
+in the `Content-Length` header and don't close the socket afterward.
+Instead, save the socket, and if another request is made to the same server
+reuse the same socket instead of creating a new one. 
+(You'll also need to pass the `"rb"` option to `makefile` or the value reported
+by `Content-Length` might not match the length of the string you're reading.)
+This will speed up repeated requests to the same server, which are common.
 
 1-7 *Redirects*. Error codes in the 300 range request a redirect. When
 your browser encounters one, it should make a new request to the URL