Expose errno with a string.

doc/api/net.markdown

@@ -70,7 +70,7 @@ another server is already running on the requested port. One way of handling thi
 would be to wait a second and the try again. This can be done with
 
     server.on('error', function (e) {
-      if (e.errno == require('constants').EADDRINUSE) {
+      if (e.code == 'EADDRINUSE') {
         console.log('Address in use, retrying...');
         setTimeout(function () {
           server.close();

src/node.cc

@@ -71,6 +71,7 @@ static Persistent<Object> process;
 static Persistent<String> errno_symbol;
 static Persistent<String> syscall_symbol;
 static Persistent<String> errpath_symbol;
+static Persistent<String> code_symbol;
 
 static Persistent<String> rss_symbol;
 static Persistent<String> vsize_symbol;
@@ -1021,6 +1022,7 @@ Local<Value> ErrnoException(int errorno,
     syscall_symbol = NODE_PSYMBOL("syscall");
     errno_symbol = NODE_PSYMBOL("errno");
     errpath_symbol = NODE_PSYMBOL("path");
+    code_symbol = NODE_PSYMBOL("code");
   }
 
   if (path) {
@@ -1035,6 +1037,7 @@ Local<Value> ErrnoException(int errorno,
   Local<Object> obj = e->ToObject();
 
   obj->Set(errno_symbol, Integer::New(errorno));
+  obj->Set(code_symbol, estring);
   if (path) obj->Set(errpath_symbol, String::New(path));
   if (syscall) obj->Set(syscall_symbol, String::NewSymbol(syscall));
   return e;

test/simple/test-net-connect-handle-econnrefused.js

@@ -16,6 +16,7 @@ c.on('error', function(e) {
   console.error('couldn\'t connect.');
   gotError = true;
   assert.equal(require('constants').ECONNREFUSED, e.errno);
+  assert.equal('ECONNREFUSED', e.code);
 });