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dgram: make send cb act as "error" event handler
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This allows users to provide a callback that handles potential
errors resulting from a `socket.send` call. The original behavior
of emitting the error event on the socket is preserved.

Fixes: nodejs/node-v0.x-archive#4846
PR-URL: nodejs/node-v0.x-archive#7738
PR-URL: #1796
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
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chrisdickinson authored and rvagg committed Aug 4, 2015
1 parent 3b021ef commit 3da057f
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Showing 3 changed files with 66 additions and 2 deletions.
4 changes: 3 additions & 1 deletion doc/api/dgram.markdown
Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,9 @@ assigned a random port number and is bound to the "all interfaces" address
An optional callback may be specified to detect DNS errors or for determining
when it's safe to reuse the `buf` object. Note that DNS lookups delay the time
to send for at least one tick. The only way to know for sure that the datagram
has been sent is by using a callback.
has been sent is by using a callback. If an error occurs and a callback is given,
the error will be the first argument to the callback. If a callback is not given,
the error is emitted as an `'error'` event on the `socket` object.

With consideration for multi-byte characters, `offset` and `length` will
be calculated with respect to
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10 changes: 9 additions & 1 deletion lib/dgram.js
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Expand Up @@ -300,7 +300,15 @@ Socket.prototype.send = function(buffer,

self._handle.lookup(address, function(ex, ip) {
if (ex) {
if (callback) callback(ex);
if (callback) {
callback(ex);

if (self.listeners('error').length)
self.emit('error', ex);

return;
}

self.emit('error', ex);
} else if (self._handle) {
var req = new SendWrap();
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54 changes: 54 additions & 0 deletions test/simple/test-dgram-send-cb-quelches-error.js
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@@ -0,0 +1,54 @@
// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

var common = require('../common');
var assert = require('assert');
var dgram = require('dgram');
var dns = require('dns');

var socket = dgram.createSocket('udp4');
var buffer = new Buffer('gary busey');
var times = 0;

dns.setServers([]);

// assert that:
// * callbacks act as "error" listeners if given.
// * callbacks and error events are emitted in a certain order.
socket.send(buffer, 0, buffer.length, 100, 'dne.example.com', callbackOnly);

function callbackOnly(err) {
assert.ok(err);
socket.once('error', onEvent);
socket.send(buffer, 0, buffer.length, 100, 'dne.example.com', onCallback);
}

function onEvent(err) {
assert.ok(err);
assert.equal(times, 0);
times++;
}

function onCallback(err) {
assert.ok(err);
assert.equal(times, 1);
socket.close();
}

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