fixed problems with simultaneous pair creation

.gitignore

@@ -0,0 +1 @@
+node_modules/

lib/socket-pair.js

@@ -1,15 +1,15 @@
 'use strict';
 
-var server;
-var listening = false;
-var sock;
+var PromiseA = require('bluebird');
+var promises = {};
 
-function createServer(cb, prefix) {
+function createServer(prefix) {
 	var os = require('os');
 	var net = require('net');
 	var path = require('path');
-  var sockname = (prefix || 'node-socket-pair') + '.' + require('crypto').randomBytes(16).toString('hex') + '.sock';
+  var sockname = prefix + '.' + require('crypto').randomBytes(16).toString('hex') + '.sock';
 
+  var sock;
   if (/^win/.test(os.platform())) {
     sock = path.join('\\\\?\\pipe', process.cwd(), sockname);
   }
@@ -17,52 +17,67 @@ function createServer(cb, prefix) {
     sock = path.join(os.tmpdir(), sockname);
   }
 
-  server = net.createServer();
-  function onServerError(err) {
-    cb(err);
-  }
-  server.once('error', onServerError);
-  server.once('listening', function () {
-    listening = true;
-    server.removeListener('error', onServerError);
+  var server = net.createServer({allowHalfOpen: true});
+  promises[prefix] = new PromiseA(function (resolve, reject) {
+    server.once('error', reject);
+
+    server.listen(sock, function () {
+      server.removeListener('error', reject);
+      resolve({sock: sock, server: server});
+    });
   });
+
+  server.on('close', function () {
+    delete promises[prefix];
+  });
+
+  return promises[prefix];
 }
 
 exports.create = function create(cb, prefix) {
+  prefix = prefix || 'node-socket-pair';
 	var net = require('net');
-	var client = new net.Socket();
+	var client = new net.Socket({allowHalfOpen: true});
 
-  function createConnection() {
-    function onClientError(err) {
-      cb(err);
-    }
-    client.connect(sock, function () {
-      client.removeListener('error', onClientError);
+  if (!promises[prefix]) {
+    createServer(prefix);
+  }
+
+  // We chain the promises to make sure that we never have multiple pending connections at
+  // the same time to make sure the pairs are always matched correctly. Otherwise two different
+  // `onConn` listeners might end up with the same connection.
+  promises[prefix] = promises[prefix].then(function (result) {
+    return new PromiseA(function (resolve) {
+      function onConn(conn) {
+        cb(null, conn);
+        resolve(result);
+      }
+      result.server.once('connection', onConn);
+
+      function onErr(err) {
+        result.server.removeListener('connection', onConn);
+        cb(err);
+        resolve(result);
+      }
+      client.once('error', onErr);
+      client.connect(result.sock, function () {
+        client.removeListener('error', onErr);
+      });
     });
-    client.once('error', onClientError);
-  }
-
-	// This server listens on a Unix socket or Windows pipe at 'sock'
-  if (!server) {
-    createServer(cb, prefix);
-  }
-
-  server.once('connection', function onEach(connection) {
-    cb(null, connection);
+  }, function (err) {
+    cb(err);
+    return PromiseA.reject(err);
   });
 
-  if (!listening) {
-    server.listen(sock, createConnection);
-  }
-  else {
-    createConnection();
-  }
-
   return client;
 };
 
 exports.closeAll = function () {
-  if (server) {
-    server.close();
-  }
+  Object.keys(promises).forEach(function (key) {
+    promises[key].then(function (result) {
+      result.server.close();
+    }, function () {
+      delete promises[key];
+    });
+  });
 };

package.json

@@ -23,5 +23,8 @@
     "writer"
   ],
   "author": "AJ ONeal <aj@daplie.com> (https://coolaj86.com)",
-  "license": "MIT OR Apache-2.0"
+  "license": "MIT OR Apache-2.0",
+  "dependencies": {
+    "bluebird": "^3.5.0"
+  }
 }