made max concurrent transfers a CLI option instead of a constant, imp…

…roved input validation

src/main.rs

@@ -125,7 +125,6 @@ impl Termination for Error {
 #[derive(Parser, Clone, Debug)]
 struct Options {
  #[clap(
- short,
  long = "mode",
  hide = true, // the user does not need to set this
  default_value = "local"
@@ -363,25 +362,30 @@ async fn main() -> Result<()> {
  panic!("end port must be greater than start port")
  }
 
- let port_count = options.end_port - options.start_port;
+ let port_count = options.end_port - options.start_port + 1;
 
- if port_count < options.threads {
+ if port_count < 3 {
+ panic!("a minimum of three ports are required")
+ } else if port_count - 2 < options.threads {
  warn!(
  "{} ports < {} threads. decreasing threads to {}",
- port_count, options.threads, port_count
+ port_count - 2,
+ options.threads,
+ port_count - 2
  );
- options.threads = port_count;
- } else if port_count < 3 {
- panic!("a minimum of three ports are required")
- } else if port_count > options.threads {
+ options.threads = port_count - 2;
+ } else if port_count - 2 > options.threads {
+ let new_end = options.start_port + options.threads + 1;
+
  warn!(
- "{} ports > {} threads. changing port range to {}-{}",
- port_count,
+ "{} ports > {} threads. changing to {}-{}",
+ port_count - 2,
  options.threads,
  options.start_port,
- options.start_port + options.threads
+ new_end
  );
- options.end_port = options.start_port + options.threads;
+
+ options.end_port = new_end;
  }
 
  if options.destination.host.is_none() && options.source.host.is_none() {