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p-server.c

@@ -211,6 +211,9 @@ int send_response(int sock,int fd, uint8_t * buf, size_t bufsize){
 #endif
     return 0;
 }
+/** print help message
+ * arg `n`: executable name
+ */
 const char * help(const char * n){
     const char * msg = "USASE : %s [Option] ...\n"
     "Options and arguments: \n"
@@ -219,7 +222,8 @@ const char * help(const char * n){
     printf(msg,n);
     return msg;
 }
-/** return 0 ok. otherwise invalid format*/
+/** parse arguments. 
+ * if return 0, success. otherwise arguments are invalid format.*/
 int parse_args(int argc,const char * argv[] , in_port_t * port){
     int pos = 1;
     const char * opt;
@@ -236,10 +240,14 @@ int parse_args(int argc,const char * argv[] , in_port_t * port){
                 const char * value = argv[pos++];
                 *port = atoi(value);
                 if (port == 0){ // either not number or zero 
+                    fprintf(stderr,"port argument is either not number or zero\n");
                     return 2;
                 }
             }
-            else return 2; //failed to find argument.
+            else{
+                fprintf(stderr,"need argument\n"); 
+                return 2; //failed to find argument.
+            }
         }
     }
     return 0;