dns: update lookupService() first arg name

The first argument to lookupService() should be an IP address,
and is named "address" in the documentation. This commit updates
the code to match the documentation and provide less confusing
errors.

lib/dns.js

@@ -164,13 +164,12 @@ function onlookupservice(err, hostname, service) {
 }
 
 
-// lookupService(address, port, callback)
-function lookupService(hostname, port, callback) {
+function lookupService(address, port, callback) {
   if (arguments.length !== 3)
-    throw new ERR_MISSING_ARGS('hostname', 'port', 'callback');
+    throw new ERR_MISSING_ARGS('address', 'port', 'callback');
 
-  if (isIP(hostname) === 0)
-    throw new ERR_INVALID_OPT_VALUE('hostname', hostname);
+  if (isIP(address) === 0)
+    throw new ERR_INVALID_OPT_VALUE('address', address);
 
   if (!isLegalPort(port))
     throw new ERR_SOCKET_BAD_PORT(port);
@@ -182,12 +181,12 @@ function lookupService(hostname, port, callback) {
 
   const req = new GetNameInfoReqWrap();
   req.callback = callback;
-  req.hostname = hostname;
+  req.hostname = address;
   req.port = port;
   req.oncomplete = onlookupservice;
 
-  const err = cares.getnameinfo(req, hostname, port);
-  if (err) throw dnsException(err, 'getnameinfo', hostname);
+  const err = cares.getnameinfo(req, address, port);
+  if (err) throw dnsException(err, 'getnameinfo', address);
   return req;
 }
 

lib/internal/dns/promises.js

@@ -151,17 +151,17 @@ function createLookupServicePromise(hostname, port) {
   });
 }
 
-function lookupService(hostname, port) {
+function lookupService(address, port) {
   if (arguments.length !== 2)
-    throw new ERR_MISSING_ARGS('hostname', 'port');
+    throw new ERR_MISSING_ARGS('address', 'port');
 
-  if (isIP(hostname) === 0)
-    throw new ERR_INVALID_OPT_VALUE('hostname', hostname);
+  if (isIP(address) === 0)
+    throw new ERR_INVALID_OPT_VALUE('address', address);
 
   if (!isLegalPort(port))
     throw new ERR_SOCKET_BAD_PORT(port);
 
-  return createLookupServicePromise(hostname, +port);
+  return createLookupServicePromise(address, +port);
 }
 
 

test/parallel/test-dns.js

@@ -265,29 +265,29 @@ dns.lookup('', {
   const err = {
     code: 'ERR_MISSING_ARGS',
     type: TypeError,
-    message: 'The "hostname", "port", and "callback" arguments must be ' +
+    message: 'The "address", "port", and "callback" arguments must be ' +
     'specified'
   };
 
   common.expectsError(() => dns.lookupService('0.0.0.0'), err);
-  err.message = 'The "hostname" and "port" arguments must be specified';
+  err.message = 'The "address" and "port" arguments must be specified';
   common.expectsError(() => dnsPromises.lookupService('0.0.0.0'), err);
 }
 
 {
-  const invalidHost = 'fasdfdsaf';
+  const invalidAddress = 'fasdfdsaf';
   const err = {
     code: 'ERR_INVALID_OPT_VALUE',
     type: TypeError,
-    message: `The value "${invalidHost}" is invalid for option "hostname"`
+    message: `The value "${invalidAddress}" is invalid for option "address"`
   };
 
   common.expectsError(() => {
-    dnsPromises.lookupService(invalidHost, 0);
+    dnsPromises.lookupService(invalidAddress, 0);
   }, err);
 
   common.expectsError(() => {
-    dns.lookupService(invalidHost, 0, common.mustNotCall());
+    dns.lookupService(invalidAddress, 0, common.mustNotCall());
   }, err);
 }