Cannot access Mac from another local Mac or iPhone on same router

[belvdr]

I could do these things all day long and if you don't like the results you will ask me to try something else. I am not the one having issues, nor did I come here seeking help. I have done everything above before and when I upgraded to Lion Server the mail stopped working for some odd reason. Spent hours on the phone with Apple 3rd level support, and nothing could be found wrong. The mail server just started working again the next day after no changes. I get all of the correct name resolutions and such, so I don't see what the big deal here is that everyone feels the need to probe my network? When I do what is asked and provide screen shots, I am told it is not working right, yet I am having no issues and have had no issues, so why the concern really?

You're making assumptions and, likely so, because you know you're wrong. You provided little detail and I'm willing to admit I'm wrong, if you can prove it. That's all any of us are saying. If you can prove what you're saying, then we'll accept it and will have learned something new!

You're providing incorrect information on how to troubleshoot the issue. Someone else may have issues similar to this in the future and read your posts and believe what you're saying. But it is simply not true.

Since you feel like providing incorrect information and won't back it up, I'll do the work for you.

Here's an example from my 10.7.2 machine:

The ping utility uses the ICMP protocol's mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from a host or gateway.

ECHO_REQUEST datagrams (``pings'') have an IP and ICMP header, followed by a ``struct timeval'' and then an arbitrary number of ``pad'' bytes used to fill out the packet.

And a ping test:

mini:~ user$ ping 172.16.6.254
PING 172.16.6.254 (172.16.6.254): 56 data bytes
64 bytes from 172.16.6.254: icmp_seq=0 ttl=255 time=0.641 ms
64 bytes from 172.16.6.254: icmp_seq=1 ttl=255 time=0.410 ms
^C
--- 172.16.6.254 ping statistics ---
2 packets transmitted, 2 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.410/0.525/0.641/0.115 ms

mini:~ user$ ping 172.16.6.254:80
ping: cannot resolve 172.16.6.254:80: Unknown host

mini:~ user$ ping 172.16.6.254:443
ping: cannot resolve 172.16.6.254:443: Unknown host

This is pinging one of my local devices which has TCP 80 and 443 open. Note the error message "Unknown host". This is proving that it is trying to resolve it as a string and not connect to a port. You are using OpenDNS too. How do I know? Because reverse DNS on the IP you list in your ping stats points there.

Since my DNS provider doesn't provide extra services (actually I use OpenDNS too, have registered, and disabled this feature), such as helping you find what you're looking for when you make a typo, it simply returns "Unknown host".

Thus your statement about using ping to resolve port issues is clearly not accurate.

 

[jasonvp]

This is pinging one of my local devices which has TCP 80 and 443 open. Note the error message "Unknown host". This is proving that it is trying to resolve it as a string and not connect to a port. Since my DNS provider doesn't provide extra services, such as helping you find what you're looking for when you make a typo, it simply returns "Unknown host".

For those that may be curious to learn more about this, what's going on here is the following:

The ping application is receiving input from belvdr that it checks internally to see whether it's a string (ie, hostname) or an IP address. It only recognizes 4 period-separated integers between 0 and 255 as valid parts of an IP address.

Anything else it sees as input is considered either a switch (prefaced with a dash) or a hostname.

That part is key. If ping doesn't recognize the input as a switch or an IP address, it takes that input and makes a C system call: gethostbyname(). When it does that, the OS' resolver takes over and queries DNS for that same input (there's a LOT I'm glossing over here, but it's not important). Assuming the DNS server can resolve the input, it'll return an IP address to the system call, and the system call will then return the IP address to ping.

Then ping crafts the ICMP ECHO_REQUEST packets to the IP address.

If the DNS server can't resolve the address, it returns NXDOMAIN. In other words: No such domain. When ping gets that error, it responds to the user: Unknown host which is easier for a person to read than NXDOMAIN is.

The assumption he and I are making here is that squeakr's DNS server is somehow setup to NOT return NXDOMAIN. Rather it returns a statically configured IP address for anything it can't resolve. Which is why it looks like ping is working when he enters that IP and port combination.

Ping isn't the right tool for the job here.

jas (+20 year UNIX hack and network engineer)

 

[belvdr]

The assumption he and I are making here is that squeakr's DNS server is somehow setup to NOT return NXDOMAIN. Rather it returns a statically configured IP address for anything it can't resolve. Which is why it looks like ping is working when he enters that IP and port combination.

It's not an assumption; it's a fact, as proven above. Many ISP DNS servers, including OpenDNS by default, look at a string and if it doesn't resolve (i.e. NXDOMAIN) it forwards you off to a search service of sorts in order to help you find what you're looking for.

If your ISP does this, you can potentially request that they disable it. In the case of OpenDNS, if you register, you can disable that feature.

 

[jasonvp]

Many ISP DNS servers, including OpenDNS by default, look at a string and if it doesn't resolve (i.e. NXDOMAIN) it forwards you off to a search service of sorts in order to help you find what you're looking for.

That makes the baby Jesus cry. A lot. Bleah. Good to know that it can be disabled on request.

jas

 

[squeakr]

You're making assumptions and, likely so, because you know you're wrong. You provided little detail and I'm willing to admit I'm wrong, if you can prove it. That's all any of us are saying. If you can prove what you're saying, then we'll accept it and will have learned something new!

Thus your statement about using ping to resolve port issues is clearly not accurate.

Thank you "ole god of the computers and all that is right and good in the world". I stated what I can prove on my system. I have posted the screen shots of pings through Terminal and the Network Utility. I am sorry those are not good enough for you that I need to jump through further hoops to prove something to you. I did not try to offer assistance so that I could be called to the carpet for what my system is doing. My statement came not from my interpretation of what ping does but rather copied directly from what was found on the web regarding how ping works (and it also supported my system's results).

I am not sure why you feel that you need to prove everyone wrong. This is not a winner take all competition. I never said you were wrong (but you have repeatedly told me that I am wrong and that I know I am, yet unwilling to acknowledge it). I made a statement and backed it with findings from my system (do you believe that I am fabricating this screen shot, hence why I need to jump through further hoops)?

To All who may read this in the future: "I AM CONTINUALLY WRONG AND KNOW NOTHING! EVERYTHING I HAVE EVER SUGGESTED IS A LIE AND MADE UP THROUGH MY IMAGINATION SOLELY!"

I hope this satisfies you and in the future will be very leary of offering any sort of help to you, as you are not very keen to anything that anyone else might offer in the way of a solution and only look to prove them wrong. I know this sounds petty and such, but I stated many times that I was not willing to pursue this any further and was having no issues with my system, yet you persist in making issues about my character, in that I am not willing to perform everything you asked as it would prove me wrong, and that is not the case. It is more to the fact that I don't care and am having no issues, so I don't feel the need, as stated before yet you continue to push the issue.

I am done with this now and good day to you. Hopefully someday you can see that there are better ways to deal with people than questions everything they say (you even quoted the other poster and corrected their statements as well).

 

[jasonvp]

Thank you "ole god of the computers and all that is right and good in the world". I stated what I can prove on my system.

Allow me to point out a quote from you earlier in the thread that start this whole sub-thread and argument. Ready?

Ping can be directed at a specific port and will work that way. I have used it several times to resolve issues with access to ports.

It simply can't, and that was mine and belvdr's point. Other tools can do that, but ping can't. You were mistaken and now, unfortunately, you're acting like a child because no matter how much he and I tried to correct you, you wouldn't have it.

You have a lot of stuff to learn about UNIX, networking, etc. So: learn it! It's fun and interesting stuff, and there are lots of resources out there to do so. But I'd recommend that you not try acting like a resource yourself because you don't understand what's going on with your system.

(you even quoted the other poster and corrected their statements as well).

Because I misspoke. I'm not up in arms about it. I'm big enough to accept there was something I didn't know (I made an ASSumption about it though).

jas

 

[squeakr]

You were mistaken and now, unfortunately, you're acting like a child because no matter how much he and I tried to correct you, you wouldn't have it.

Sorry I was mistaken. Based upon what I found within the definition of ping and how my system reacts, it was working as I described. The statement you quoted never stated it was a fact or that I even thought it such, but am being treated as though I did. I stated something, when questioned about how could it be happening, I provided the proof of it happening based upon the way my systems reacted. Is it unreasonable to assume that since the definition I found stated it performed that way and since it did such on all of my systems (not just one, tried it on 3 different systems) that it would perform the same on others?

I am sorry if you feel that I am acting like a child, but I stated what I had found, provided my backing, yet the other poster proceeds to challenge me to prove otherwise, even after I stated that I had no interest in pursuing the matter. He then proceeds to attack my character and challenge my findings claiming falsehoods such as I know that I am wrong, just won't admit it because I know I am wrong. I did nothing to provoke this, yet I am the child??

I am being petty and will admit it, but I felt no other reproach, and this was meant in no way towards you. I appreciate the way that you handled the situation without being condescending and accusatory. Had I not been attacked (or at least made to feel such way by the other poster) I might have been more receptive to continue the discussion. Explain how it helps the situation when someone whom offers no help or solutions comes into a thread and just puts another users suggestions down? Did you need the help backing your point, as the other poster feels you did and felt the need to correct you as well (although in a much nicer way than he treated me).

I never offered these as solutions just trouble shooting tools. I have been a technician for years and have found in my many years that sometimes the unconventional approach is in fact the one that reveals the solution.

I am sorry if I offended or offset you, as that was not the intent. I just don't feel that I deserved the attitude received from the other poster.

 

[belvdr]

Thank you "ole god of the computers and all that is right and good in the world". I stated what I can prove on my system. I have posted the screen shots of pings through Terminal and the Network Utility. I am sorry those are not good enough for you that I need to jump through further hoops to prove something to you. I did not try to offer assistance so that I could be called to the carpet for what my system is doing. My statement came not from my interpretation of what ping does but rather copied directly from what was found on the web regarding how ping works (and it also supported my system's results).

I am not sure why you feel that you need to prove everyone wrong. This is not a winner take all competition. I never said you were wrong (but you have repeatedly told me that I am wrong and that I know I am, yet unwilling to acknowledge it). I made a statement and backed it with findings from my system (do you believe that I am fabricating this screen shot, hence why I need to jump through further hoops)?

To All who may read this in the future: "I AM CONTINUALLY WRONG AND KNOW NOTHING! EVERYTHING I HAVE EVER SUGGESTED IS A LIE AND MADE UP THROUGH MY IMAGINATION SOLELY!"

I hope this satisfies you and in the future will be very leary of offering any sort of help to you, as you are not very keen to anything that anyone else might offer in the way of a solution and only look to prove them wrong. I know this sounds petty and such, but I stated many times that I was not willing to pursue this any further and was having no issues with my system, yet you persist in making issues about my character, in that I am not willing to perform everything you asked as it would prove me wrong, and that is not the case. It is more to the fact that I don't care and am having no issues, so I don't feel the need, as stated before yet you continue to push the issue.

I am done with this now and good day to you. Hopefully someday you can see that there are better ways to deal with people than questions everything they say (you even quoted the other poster and corrected their statements as well).

Now that you have that out of your system, let's proceed. The screenshots are useful and I believe they are valid. However there's information there you're missing. Yes, you're pinging and receiving replies. But (and it's an important but!), you're pinging the IP 192.168.1.5, but you're not getting replies from it. You're getting replies from elsewhere. Aha! So you'll never send a ping to one IP and get a reply from another, unless something screwy is going on.

So now, onward and upward!

Sorry I was mistaken. Based upon what I found within the definition of ping and how my system reacts, it was working as I described. The statement you quoted never stated it was a fact or that I even thought it such, but am being treated as though I did. I stated something, when questioned about how could it be happening, I provided the proof of it happening based upon the way my systems reacted. Is it unreasonable to assume that since the definition I found stated it performed that way and since it did such on all of my systems (not just one, tried it on 3 different systems) that it would perform the same on others?

I'm not sure where you got that definition, but it is inaccurate. The most accurate definition of what a tool does would be the man page (or help page) on the operating system in question. Case in point, you took that little nugget from the Internet as truth, and since you stated it here as truth, I felt obliged to point out that it was not. It has nothing to do with you personally.

I am sorry if you feel that I am acting like a child, but I stated what I had found, provided my backing, yet the other poster proceeds to challenge me to prove otherwise, even after I stated that I had no interest in pursuing the matter. He then proceeds to attack my character and challenge my findings claiming falsehoods such as I know that I am wrong, just won't admit it because I know I am wrong. I did nothing to provoke this, yet I am the child??

I certainly don't recall attacking your character, even after re-reading through the thread. My apologies if you took it that way; words on the Internet don't necessarily translate well without facial expressions and such. When we asked you to perform some simple tests, you went on the defensive and wouldn't even do it. Did I ask just to belittle you? Heavens no! I asked simply because I really enjoy computer networking and if your system is doing something much different than others, I can see why. It's all a matter of learning for everyone involved.

Many times, when troubleshooting an issue at work, I find all sorts of contradictions about what is happening and why. I'm always appreciative when someone steps in and shows proof of what's going on. Why? Because that's how people learn for themselves. It's not a "take this statement as fact"; it's "here's the proof, therefore it is fact."

I am being petty and will admit it, but I felt no other reproach, and this was meant in no way towards you. I appreciate the way that you handled the situation without being condescending and accusatory. Had I not been attacked (or at least made to feel such way by the other poster) I might have been more receptive to continue the discussion. Explain how it helps the situation when someone whom offers no help or solutions comes into a thread and just puts another users suggestions down? Did you need the help backing your point, as the other poster feels you did and felt the need to correct you as well (although in a much nicer way than he treated me).

I explained how it helps above. There are many statements on the Internet that are believed to be true, but are not. So what happens if someone else has a similar issue and stumbles upon this thread without my involvement? They're going to think they can test port connectivity with ping, which is not true. I wasn't coming in just to put you down; there's no point in doing so. I was stepping in to provide some guidance on why using ping to test ports is not the correct approach.

The reason I corrected jasonvp was to point out that it's not assuming the DNS servers are trying to assist you. It was proven in the tests I performed. Like I said, we can all learn together. I've been schooled many times by others. It's a part of life for everyone as there's not a single person who knows it all.

I never offered these as solutions just trouble shooting tools. I have been a technician for years and have found in my many years that sometimes the unconventional approach is in fact the one that reveals the solution.

True, but what you were offering wasn't a valid troubleshooting technique. As a technician, surely you can appreciate it when someone brings something extra to the table, no?

I am sorry if I offended or offset you, as that was not the intent. I just don't feel that I deserved the attitude received from the other poster.

I meant no attitude. Honestly, I felt you were getting an attitude (maybe not the best word, but mainly being defensive as if I was attacking) as well when it was suggested you a few commands. That's when I figured I would show the results of a few commands.

It's not a "hey I'm right, you're wrong" scenario; it's not a zero sum game. That's not at all how I work. We can all learn together, so just calm down and realize that there was no attacking at all coming from me.

Life's too short to worry about what others on the Internet are saying.

 

[squeakr]

Now that you have that out of your system, let's proceed.

Case in point, you took that little nugget from the Internet as truth, and since you stated it here as truth, I felt obliged to point out that it was not.

I certainly don't recall attacking your character, even after re-reading through the thread. My apologies if you took it that way; words on the Internet don't necessarily translate well without facial expressions and such. When we asked you to perform some simple tests, you went on the defensive and wouldn't even do it. Did I ask just to belittle you? Heavens no! I asked simply because I really enjoy computer networking and if your system is doing something much different than others, I can see why. It's all a matter of learning for everyone involved.

Many times, when troubleshooting an issue at work, I find all sorts of contradictions about what is happening and why. I'm always appreciative when someone steps in and shows proof of what's going on. Why? Because that's how people learn for themselves. It's not a "take this statement as fact"; it's "here's the proof, therefore it is fact."

I explained how it helps above. There are many statements on the Internet that are believed to be true, but are not. So what happens if someone else has a similar issue and stumbles upon this thread without my involvement? They're going to think they can test port connectivity with ping, which is not true. I wasn't coming in just to put you down; there's no point in doing so. I was stepping in to provide some guidance on why using ping to test ports is not the correct approach.

The reason I corrected jasonvp was to point out that it's not assuming the DNS servers are trying to assist you. It was proven in the tests I performed. Like I said, we can all learn together. I've been schooled many times by others. It's a part of life for everyone as there's not a single person who knows it all.

True, but what you were offering wasn't a valid troubleshooting technique. As a technician, surely you can appreciate it when someone brings something extra to the table, no?

I meant no attitude. Honestly, I felt you were getting an attitude (maybe not the best word, but mainly being defensive as if I was attacking) as well when it was suggested you a few commands. That's when I figured I would show the results of a few commands.

It's not a "hey I'm right, you're wrong" scenario; it's not a zero sum game. That's not at all how I work. We can all learn together, so just calm down and realize that there was no attacking at all coming from me.

Life's too short to worry about what others on the Internet are saying.

I would love to accept your apology if I in fact felt it was truthful and heartfelt, but I have to admit at this point I don't feel it.

Reread your statements above and you can see my point and why I am defensive (I'll admit it, as your choice of wording puts one on the defensive). Was the whole "got that out of your system" necessary? No it was condescending and a less than great way to start off an explanation, as was the statement "that little nugget". You are thinking you are being cute, but it is just condescending and all the smilies in the world don't take way the intent or make it cute.

The way that you write the remainder of your statements. You state that I have brought falsehoods to the table and claimed them as truths. I have done nothing of the sort as I never claimed them as truths that is your words and not mine.

I became defensive (or as you like to call attitude, once again another dig at me and then try to override by saying it was defensive. Hint could have left out the attitude if you really didn't believe that is what it was as you have stated. That just adds to the tension. Just say you seemed on the defensive, as it is much nicer than saying you have attitude.) as I had stated what I found (never called it a truth), provided the backing for my statements, and since you didn't agree you decided I needed to offer up more proof. I didn't feel that I needed to offer more as I was not asking for help. After I had said I was not going to perform any more tests, you proceeded to perform your own, and then badger me about not providing the screen shots and doing the tests as requested. You made a statement, provided the same level of proof as I did, and stated yours was the fact. I have never questioned your claims, yet you have provided the same level of proof as I have (you provided screen shots like I have so what makes your results better than mine, especially to someone who doesn't know like I don't as you have made so clear!!), yet you then go on to state I am not willing to proceed further as I know I am wrong (glad you know exactly how I think and act).

I agree that bringing other things to the table is a good thing, and sometimes doing things not exactly as prescribed works the best (say the OP had followed my lead and got the same results I did, would you not have had better ideals about what was wrong with the system, or had they received the correct results, we know that something can then be ruled out as it is working correctly?) this has helped me to fix issues quicker in some instances by looking for and doing what is wrong instead of what is correct.

Ending your whole statement with "just calm down" sounds like an order and is not friendly.

Just realize that even with your apology, you have put me on the defensive and insulted me, and this is why I am not willing to work further with you, NOT because I know I am wrong, but because I don't like be talked down to.

I love to learn new things and am learning all the time, but don't like dealing with a teacher that is condescending. You could have easily left out the snide remarks and the meaning would have come through better and would make me believe that you meant what you said, not second guess it.

 

[belvdr]

I would love to accept your apology if I in fact felt it was truthful and heartfelt, but I have to admit at this point I don't feel it.

Well, considering you misconstrued my other comments as attacking (and they really were not meant to be), this doesn't surprise me. I admit I don't understand how one can feel the emotions from an apology with just words on a screen.

Reread your statements above and you can see my point and why I am defensive (I'll admit it, as your choice of wording puts one on the defensive). Was the whole "got that out of your system" necessary? No it was condescending and a less than great way to start off an explanation, as was the statement "that little nugget". You are thinking you are being cute, but it is just condescending and all the smilies in the world don't take way the intent or make it cute.

Just as you say I don't know what you're thinking, you have no idea of my intent, including whether I was "trying to be cute" (Hint: I wasn't). I already told you I re-read everything and don't see an issue. It looks to me like statements, nothing more, nothing less.

The way that you write the remainder of your statements. You state that I have brought falsehoods to the table and claimed them as truths. I have done nothing of the sort as I never claimed them as truths that is your words and not mine.

Yes, you did. You were even quoted above, and I'll quote it again:

Ping can be directed at a specific port and will work that way. I have used it several times to resolve issues with access to ports.

and then:

The ping utility within Mac allows it. The OP is on Mac and having issues with Mac hence the recommendation to use the ping utility in Mac (which it works on).

Correct in that the classic version does not, but the utility within Mac does.

That's what you claim is true and it isn't. It's pretty cut and dry.

I became defensive (or as you like to call attitude, once again another dig at me and then try to override by saying it was defensive. Hint could have left out the attitude if you really didn't believe that is what it was as you have stated. That just adds to the tension. Just say you seemed on the defensive, as it is much nicer than saying you have attitude.) as I had stated what I found (never called it a truth), provided the backing for my statements, and since you didn't agree you decided I needed to offer up more proof. I didn't feel that I needed to offer more as I was not asking for help. After I had said I was not going to perform any more tests, you proceeded to perform your own, and then badger me about not providing the screen shots and doing the tests as requested. You made a statement, provided the same level of proof as I did, and stated yours was the fact. I have never questioned your claims, yet you have provided the same level of proof as I have (you provided screen shots like I have so what makes your results better than mine, especially to someone who doesn't know like I don't as you have made so clear!!), yet you then go on to state I am not willing to proceed further as I know I am wrong (glad you know exactly how I think and act).

I specifically went to the man page of ping, from OS X, and showed how it used ICMP only. I also provided more information on what is going on ("192.168.1.5:443" is being queried in DNS instead of being treated like an IP). You can see this in your screenshot where it says "192.168.1.5:443 (67.215.64.132)". That's telling you DNS resolved it, otherwise you'd have the same IP in both fields, as in my code. You posted your screenshots as proof, but it has been stated and proven that you are misreading the information you provided. If you can't take a look at what I've stated and see how your statements are inaccurate, then you don't have a thorough understanding of what you posted. All I did was point it out to you.

There are utilities to test whether TCP/UDP ports are open, such as nmap, which was stated above. Yet, you continue to argue the point that ping does this, when proof has been given otherwise. If you don't believe my proof, why not come back with some additional information instead of ranting/venting? That's certainly not a way to learn new things.

I agree that bringing other things to the table is a good thing, and sometimes doing things not exactly as prescribed works the best (say the OP had followed my lead and got the same results, would you not have had better ideals about what was wrong with the system, or had they received the correct results, we know that something can then be ruled as it is working correctly?) this has helped me to fix issues quicker in some instances by looking for what is wrong instead of what is correct.

Well, looking for what is wrong by using a tool incorrectly doesn't really help though. If the OP had done what you had suggested, it would have proven nothing, other than whether his DNS provider provides assistance for typos.

Ending your whole statement with "just calm down" is an order and is not friendly either.

Yeah, that was an order. If you would put it back in context, you'd realize I was just making a statement of how I wasn't attacking you.

Just realize that even with your apology, you have put me on the defensive and insulted me, and this is why I am not willing to work further with you, NOT because I know I am wrong, but because I don't like be talked down to.

I love to learn new things and am learning all the time, but don't like dealing with a teacher that is condescending. You could have easily left out half of the snide remarks and I would have felt much better

You're being overly sensitive. There were no snide remarks; you're just reading that into it. It seems like you just can't handle criticism. Yes, I'm blunt and you just can't expect for everyone to deliver criticism in a format that you desire.

If you don't want to accept my apology, so be it. Good day!