Default to dual stack and add BIND arg

Change the default bind address to be `[::]` and allow the user to
specify the socket to bind on.

This is distinct from the HOST/PORT pair already configurable as phd
might be running behind a proxy where links need to be generated with a
different destination to the bound socket.

doc/phd.1

@@ -1,10 +1,11 @@
-.\" Generated by scdoc 1.10.0
+.\" Generated by scdoc 1.11.0
+.\" Complete documentation for this program is not available as a GNU info page
 .ie \n(.g .ds Aq \(aq
 .el       .ds Aq '
 .nh
 .ad l
 .\" Begin generated content:
-.TH "PHD" "1" "2020-05-09"
+.TH "PHD" "1" "2020-06-27"
 .P
 .SH NAME
 .P
@@ -41,6 +42,11 @@ of your Gopher site.
 Rather than start as a server, render the \fISELECTOR\fR of the site using the options provided and print the raw response to \fBSTDOUT\fR.
 .P
 .RE
+\fB-b\fR \fIADDRESS\fR, \fB--bind\fR \fIADDRESS\fR
+.RS 4
+Set the socket address to bind to, e.g. \fB127.0.0.1:7070\fR
+.P
+.RE
 \fB-p\fR \fIPORT\fR, \fB--port\fR \fIPORT\fR
 .RS 4
 Set the \fIPORT\fR to use when generating Gopher links.

doc/phd.1.md

@@ -31,6 +31,9 @@ of your Gopher site.
 
 	Rather than start as a server, render the _SELECTOR_ of the site using the options provided and print the raw response to *STDOUT*.
 
+*-b* _ADDRESS_, *--bind* _ADDRESS_
+	Set the socket address to bind to, e.g. *127.0.0.1:7070*
+
 *-p* _PORT_, *--port* _PORT_
 	Set the _PORT_ to use when generating Gopher links.
 

src/main.rs

@@ -1,6 +1,8 @@
 use phd;
 use std::process;
+use std::net::SocketAddr;
 
+const DEFAULT_BIND: &str = "[::]:7070";
 const DEFAULT_HOST: &str = "127.0.0.1";
 const DEFAULT_PORT: u16 = 7070;
 
@@ -8,6 +10,7 @@ fn main() {
     let args = std::env::args().skip(1).collect::<Vec<_>>();
     let mut args = args.iter();
     let mut root = ".";
+    let mut bind: SocketAddr = DEFAULT_BIND.parse().unwrap();
     let mut host = DEFAULT_HOST;
     let mut port = DEFAULT_PORT;
     let mut render = "";
@@ -22,6 +25,17 @@ fn main() {
                     render = "/";
                 }
             }
+            "--bind" | "-b" | "-bind" => {
+                if let Some(b) = args.next() {
+                    bind = b
+                        .parse()
+                        .map_err(|_| {
+                            eprintln!("bad socket bind: {}", b);
+                            process::exit(1)
+                        })
+                        .unwrap();
+                }
+            }
             "--port" | "-p" | "-port" => {
                 if let Some(p) = args.next() {
                     port = p
@@ -63,7 +77,7 @@ fn main() {
         };
     }
 
-    if let Err(e) = phd::server::start(host, port, root) {
+    if let Err(e) = phd::server::start(bind, host, port, root) {
         eprintln!("{}", e);
     }
 }

src/server.rs

@@ -5,7 +5,7 @@ use std::{
     cmp::Ordering,
     fs::{self, DirEntry},
     io::{self, prelude::*, BufReader, Read, Write},
-    net::{TcpListener, TcpStream},
+    net::{SocketAddr, TcpListener, TcpStream},
     os::unix::fs::PermissionsExt,
     path::Path,
     process::Command,
@@ -50,9 +50,8 @@ macro_rules! info {
 }
 
 /// Starts a Gopher server at the specified host, port, and root directory.
-pub fn start(host: &str, port: u16, root: &str) -> Result<()> {
+pub fn start(bind: SocketAddr, host: &str, port: u16, root: &str) -> Result<()> {
-    let addr = format!("{}:{}", "0.0.0.0", port);
+    let listener = TcpListener::bind(&bind)?;
-    let listener = TcpListener::bind(&addr)?;
     let full_root_path = fs::canonicalize(&root)?.to_string_lossy().to_string();
     let pool = ThreadPool::new(MAX_WORKERS);
 
@@ -61,7 +60,7 @@ pub fn start(host: &str, port: u16, root: &str) -> Result<()> {
         color::Yellow,
         color::Reset,
         color::Yellow,
-        addr,
+        bind,
         color::Reset,
         color::Blue,
         full_root_path,