Larry, You are missing a bit of important code from the example in the blog post.
In his original example, "echo" is a function (note the code block that begins, (defn echo ...). His "listen-and-respond" function is what handles reading from the ServerSocket, and responding back on the socket with the output (the result of callin the service function). The ServerSocket constructor he invokes takes a single argument, the port number. There is no constructor that takes a hostname as a string, which is where all your attempts are failing (as you can see from the javadoc for ServerSocket here: http://docs.oracle.com/javase/1.4.2/docs/api/java/net/ServerSocket.html). Also, trying to take the "what-to-do" command line parameter and treat it as a symbol is a total red herring. You should not normally need to use the symbol function in "typical" clojure code, it is more usually needed for macro manipulation. So: 1) Remove "localhost" from your constructor invocation. 2) Your command line argument what-to-do is kind of nonsense. "listen-and-respond" is expecting a fn as its 2nd argument For instance: (defn run-server [port what-to-do] (let [server-socket (ServerSocket. port)] (while (not (. server-socket isClosed)) (listen-and-respond server-socket what-to-do)))) # I don't know if the following works, but something close to it probably will (defn dumb-service [word] (fn [input output] (loop [line (.readLine input)] (if-not (= line "")) (recur (.readLine input)) (-> output (.println word) .flush .close))))) (defn -main [& args] (let [port (Integer/parseInt (first args)) word (second args))] (println "Server is starting") (println "port: " port) (println (second args)) (run-server port (dumb-service word)))) On Tue, Aug 28, 2012 at 8:25 PM, larry google groups <lawrencecloj...@gmail.com> wrote: > I apologize about the beginner questions. I am new to Clojure. > > If I do this: > > (defn run-server [port what-to-do] > (let [server-socket (ServerSocket. port "localhost")] > (while (not (. server-socket isClosed)) > (listen-and-respond server-socket what-to-do)))) > > (defn -main [& args] > (let [port (Integer/parseInt (first args)) > service (symbol (second args))] > (println "Server is starting") > (println "port: " port) > (println (second args)) > (println (symbol (second args))) > (println "service: " service) > (run-server port service))) > > And on the command line I call it like: > > java -jar who-is-logged-in-1.0-standalone.jar 3456 "who-is-here-now" > > This prints out: > > Server is starting > port: 3456 > who-is-here-now > who-is-here-now > service: who-is-here-now > > but then I get this error: > > Exception in thread "main" java.lang.ClassCastException: java.lang.String > cannot be cast to java.lang.Number > at who_is_logged_in.core$run_server.invoke(core.clj:27) > > Line 27 is: > > (defn run-server [port what-to-do] > > The only way I can read the error message is to think that the code is > trying to assign the value of what-to-do to the (integer) "port". > > What have I done wrong? > > > > > On Tuesday, August 28, 2012 12:47:44 PM UTC-4, larry google groups wrote: >> >> >Command line arguments that are not strings need to be converted >> > prior to use by your main function. >> >> That makes sense, I need to cast it to a symbol, yes? I have a problem >> with that though. At the REPL I tried something like this: >> >> (def hey (resolve (symbol what-to-do))) >> >> which worked great at the REPL, but in my code I get "nil" returned from >> resolve. If I do this: >> >> (defn -main [& args] >> (let [port (Integer/parseInt (first args)) >> service (resolve (symbol (second args)))] >> (println "Server is starting") >> (println "port: " port) >> (println (second args)) >> (println (symbol (second args))) >> (println "service: " service) >> (run-server port service))) >> >> And call it like this: >> >> java -jar who-is-logged-in-1.0.0-SNAPSHOT-standalone.jar 3456 >> "who-is-here-now" >> >> Everything looks correct till the final line when I get "nil": >> >> Server is starting >> port: 3456 >> who-is-here-now >> who-is-here-now >> service: nil >> >> >> >> >> >> >> >> >> On Tuesday, August 28, 2012 6:53:24 AM UTC-4, Jon_Boone wrote: >>> >>> Command line arguments that are not strings need to be converted prior to >>> use by your main function. >>> >>> Look at the code for the port number and do the same for the service. >>> >>> --jon >>> >>> >>> On Aug 28, 2012, at 2:42, larry google groups <lawrenc...@gmail.com> >>> wrote: >>> >>> >>> So, this started when I read Keith Swallow's article on a simple web >>> server: >>> >>> http://keithcelt.com/a-simple-web-server-in-clojure >>> >>> I took his code and ran "lein new" to create a new project and I copy and >>> pasted his code to core.clj and made some minor adjustments, adding >>> gen-class and main so I could run this from the command line. My main >>> function looked like this: >>> >>> (defn -main [& args] >>> (let [port (Integer/parseInt (first args))] >>> (println "Server is starting") >>> (run-server port echo))) >>> >>> Which called his function: >>> >>> (defn run-server [port service] >>> (let [server-socket (create-socket port)] >>> (while (not (. server-socket isClosed)) >>> >>> (listen-and-respond server-socket service)))) >>> >>> I compiled that and ran "lein uberjar" and then ran it from the command >>> line and it worked great. >>> >>> Then, to make it slightly more flexible, I wanted to hand in the name of >>> the service from the command line. So I made a minor change: >>> >>> >>> (defn run-server [port what-to-do] >>> (let [server-socket (ServerSocket. "localhost" port)] >>> (while (not (. server-socket isClosed)) >>> (listen-and-respond server-socket what-to-do)))) >>> >>> (defn -main [& args] >>> (let [port (Integer/parseInt (first args)) >>> service (second args)] >>> (println "Server is starting") >>> (println "port: " port) >>> (println "service: " service) >>> (run-server port service))) >>> >>> I compiled this and ran it. And now this line: >>> >>> (defn run-server [port what-to-do] >>> >>> Gets this error: >>> >>> Exception in thread "main" java.lang.ClassCastException: java.lang.String >>> cannot be cast to java.lang.Number >>> at who_is_logged_in.core$run_server.invoke(core.clj:27) >>> >>> I'm calling it from the command line with: >>> >>> java -jar who-is-logged-in-1.0.0-SNAPSHOT-standalone.jar 3456 >>> who-is-here-now >>> >>> I also tried putting the service name in quotes: >>> >>> java -jar who-is-logged-in-1.0.0-SNAPSHOT-standalone.jar 3456 >>> "who-is-here-now" >>> >>> Can anyone tell me what is wrong? Why does Clojure think I'm trying to >>> cast "who-is-here-now" to a number? >>> >>> >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "Clojure" group. >>> To post to this group, send email to clo...@googlegroups.com >>> Note that posts from new members are moderated - please be patient with >>> your first post. >>> To unsubscribe from this group, send email to >>> clojure+u...@googlegroups.com >>> For more options, visit this group at >>> http://groups.google.com/group/clojure?hl=en > > -- > You received this message because you are subscribed to the Google > Groups "Clojure" group. > To post to this group, send email to clojure@googlegroups.com > Note that posts from new members are moderated - please be patient with your > first post. > To unsubscribe from this group, send email to > clojure+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/clojure?hl=en -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
