Thanks, Arron. I have a lot to learn about discerning the meaning of the stack traces. It said line 27, but, as you point out, the real problem was on line 28.
On Tuesday, August 28, 2012 10:36:15 PM UTC-4, Aaron Cohen wrote: > > 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 > <lawrenc...@gmail.com <javascript:>> 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 clo...@googlegroups.com<javascript:> > > 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 <javascript:> > > 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. 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