net: some scattered cleanup

This commit cleans up net module, including: 1. remove assigning
`handle.readable` and `handle.writable` 2. documents
`NODE_PENDING_PIPE_INSTANCES` enviroment variable 3. use constants
for '0.0.0.0' and '::'.

PR-URL: https://github.com/nodejs/node/pull/24128
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 10 insertions, 9 deletions

diff --git a/lib/net.js b/lib/net.js
index 0e68e95400..ecf7258e8b 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -96,6 +96,9 @@ let dns;
 
 const { kTimeout } = require('internal/timers');
 
+const DEFAULT_IPV4_ADDR = '0.0.0.0';
+const DEFAULT_IPV6_ADDR = '::';
+
 function noop() {}
 
 function getFlags(ipv6Only) {
@@ -789,10 +792,10 @@ function internalConnect(
 
   if (localAddress || localPort) {
     if (addressType === 4) {
-      localAddress = localAddress || '0.0.0.0';
+      localAddress = localAddress || DEFAULT_IPV4_ADDR;
       err = self._handle.bind(localAddress, localPort);
     } else { // addressType === 6
-      localAddress = localAddress || '::';
+      localAddress = localAddress || DEFAULT_IPV6_ADDR;
       err = self._handle.bind6(localAddress, localPort, flags);
     }
     debug('binding to localAddress: %s and localPort: %d (addressType: %d)',
@@ -1145,8 +1148,6 @@ function createServerHandle(address, port, addressType, fd, flags) {
     if (err)
       return err;
 
-    handle.readable = true;
-    handle.writable = true;
     assert(!address && !port);
   } else if (port === -1 && addressType === -1) {
     handle = new Pipe(PipeConstants.SERVER);
@@ -1165,11 +1166,11 @@ function createServerHandle(address, port, addressType, fd, flags) {
     debug('bind to', address || 'any');
     if (!address) {
       // Try binding to ipv6 first
-      err = handle.bind6('::', port, flags);
+      err = handle.bind6(DEFAULT_IPV6_ADDR, port, flags);
       if (err) {
         handle.close();
         // Fallback to ipv4
-        return createServerHandle('0.0.0.0', port);
+        return createServerHandle(DEFAULT_IPV4_ADDR, port);
       }
     } else if (addressType === 6) {
       err = handle.bind6(address, port, flags);
@@ -1200,14 +1201,14 @@ function setupListenHandle(address, port, addressType, backlog, fd, flags) {
 
     // Try to bind to the unspecified IPv6 address, see if IPv6 is available
     if (!address && typeof fd !== 'number') {
-      rval = createServerHandle('::', port, 6, fd, flags);
+      rval = createServerHandle(DEFAULT_IPV6_ADDR, port, 6, fd, flags);
 
       if (typeof rval === 'number') {
         rval = null;
-        address = '0.0.0.0';
+        address = DEFAULT_IPV4_ADDR;
         addressType = 4;
       } else {
-        address = '::';
+        address = DEFAULT_IPV6_ADDR;
         addressType = 6;
       }
     }