Using sudo ping -f (URL) on a Mac gives the message:
Request timeout for icmp_seq as a reply.
How can I fix this?
The reply means the target host is unreachable which is not an error and can happen using a plain 'ping' as well.
Now, using the -f(lood) option, some firewalls or hosts can believe it's a DoS attack and drop the icmp packets silently.
Do you really need this -f option ? It can overflow the network and should be avoided as much as possible.
Related
I am connecting to a server that initiates an SSH tunnel for me so I can connect to a remote device.
I can do an interactive socat connexion and manually issue commands like this:
Connected to soundwave server v131 (welcome message)
tunnel r 7 localhost:22 (my command)
Attempting to initiate a tunnel session ID [55] on local port 30054. (response)
The text in parenthesis is just my notes. They aren't actually part of the commands or responses.
I know I can send a message to a unix socket using socat
echo "tunnel r 7 localhost:22" | socat UNIX-CONNECT:data/files/monitor.socket STDOUT
And I saw some posts about being able to write a command and read a command with socat.
But the software has limitations that it only listens for commands until after the welcome message is issued.
So, is there a way with socat, nc, or any other tool to connect to a unix socket automatically, read the welcome message, write the tunnel command, and then parse the response to get the port so I can open up an SSH session?
Thanks so much.
My daemon has option
-r WhereShouldIOutputAdditionalData
daemon is listening on port 26542 and writes on the same port , I want additional data to output to 26542 as well, I tried using
-r /dev/tcp/127.0.0.1/26542
and it doesn't work, When I do
> /dev/tcp/127.0.0.1/26542
I get connection refused. Deamon that I use: vowpal_wabbit, machine learning library.Any ideas?
Per an unoffical man page at
https://github.com/JohnLangford/vowpal_wabbit/wiki/Command-line-arguments
I see
-r [ --raw_predictions ] arg File to output unnormalized predictions to
So I think the -r argument is expecting a sort of /path/to/logs/raw_preds.log argument.
With this, you'll have "captured the optional output so it is readable." You could open a separate window and use the dev/admins old friend tail -f /path/to/logs/raw_preds.log to see info as it is written to the file.
If you really want it all to appear on one port, (which isn't exactly clear from your question), you'd need a separate program that can multi-plex the outputs, AND has control of your required port number. Also you'll need to be concerned about correct order of output.
IHTH.
I'm sorry, what you want to do it's impossibile for two reasons:
First, bash cannot listen on a given TCP port.
For example you cannot write a TCP server daemon in plain bash (you could use netcat for that), you can only connect() to a TCP port in bash.
Also, it is impossibile to listen on the same TCP ip:port that is already in LISTEN state by another process.
I have a question that is very similar to this question, but the solution provided is not working for me. And actually I want to do something a little different, so maybe there's a better way.
My hope is to send UDP unicast packets (a video stream) to a server. The server will forward these packets to another computer. Optionally, someone logged into the server will be able to watch the video stream using something like mplayer. I'm pretty sure I could stream the video both to the server and to the final destination from the video source, but I really want the server to be in control of that.
First Attempt:
Downloaded nmap to get the ncat tool. Thought I could use that to download and pipe bytes to mplayer and forward with another ncat process. I can pipe to mplayer and it works great, I just can't forward at the same time. If I was using Linux, apparently I could use tee and process substitution, but I'm looking for a Windows solution.
Second Attempt
I found a solution that kind of implied piping to multiple programs would be possible in PowerShell. But what I found is that binary piping wasn't going to work.
Third Attempt
I attempted to program a tee-like executable that would tee to two programs. This was about as close as I got, but the video streams seemed to get a bit corrupted. I think it was more of a performance issue than anything.
Fourth Attempt
Now I'm at the point where I've discovered socat which led me to the question I linked to. It seems odd, but I thought a solution would be for my server to forward packets to the destination AND forward packets to a different port on the server which would be used with netcat or socat to pipe into mplayer. I'd rather not use up another port on the server, but if that's what I have to do, then ok. But like I said, the solution from the other question didn't seem to work. Mplayer started to buffer, then stopped very shortly.
Ran each of these in a separate cmd window in this order. Notice I wasn't trying to forward to the destination computer yet, just trying to get mplayer to work on the server.
socat UDP4-LISTEN:5000 UDP-DATAGRAM:224.10.10.10:5001
socat UDP4-RECVFROM:5001,ip-add-membership=224.10.10.10:0.0.0.0,reuseaddr,fork UDP-DATAGRAM:192.168.16.33:5002
ncat -l -u -p 5002 | mplayer -vo direct3d -cache 1024 -
I seem to get about 924 bytes received according to MPlayer output.
I'm fresh out of ideas, though I will continue learning about socat. I assume I am not running socat correctly, but I'm not really sure where the issue is. If anyone can point out my mistake or offer an alternative solution I'd really appreciate it. Thanks.
Edit:
I did some more testing and if I change the second socat to do this:
socat UDP4-RECVFROM:5001,ip-add-membership=224.10.10.10:0.0.0.0,reuseaddr,fork - | mplayer -vo direct3d -cache 1024 -
I find that it will play the stream from the multicast address. But apparently forwarding to the unicast address on port 5002 is what's not working.
Ok, I'm not really sure why this is, but the netcat process that worked fine to receive the UDP packets from the sender and pipe to MPlayer does not work here. I'm not sure what the problem is.
So instead of:
ncat -l -u -p 5002 | mplayer -vo direct3d -cache 1024 -
I had to use:
socat UDP4-RECVFROM:5002,fork - | mplayer -vo direct3d -cache 1024 -
Though I do still have one small problem. If I close MPlayer, I get a ton of messages like:
2015/02/24 11:14:04 socat[5888] E write(1, 0x800432e8, 986): Broken
pipe
Also if I hit Ctrl-C from the command line it takes a few tries and then when MPlayer stops, my keyboard no longer works and I have to start a new cmd window.
I would like to simulate different ping times for the same host (my local machine with Mac OS X). For example, I would like ping localhost and ping myhostname.mydomain.com return different ping times. Can I do it ?
Can I configure a few new host names (myhost1 localhost, myhost2 localhost) in /etc/hosts and simulate different ping times for ping myhost1 and ping myhost2 ?
You could make a wrapper around ping like this.
1) rename your real ping as ping.real
2) write a new ping and store it where original ping was, and have it do a wait of a few seconds before execing ping.real depending on the parameter (IP address/or hostname).
Ok, here is an alternative method if you don't really use the ping executable... how about using LD_PRELOAD to replace the sendto() and/or recvfrom() calls and add delays in there? See example for replacing malloc() here.
I'm trying to write a server using netcat and bash. to recieve asynchronous packets, i'm using the command
netcat -lu 6791
How can I tell what host a packet came from? Is there a better tool i should be using then netcat (socat maybe?)
wireshark (GUI tool), tshark (text-based version of wireshark), and/or tcpdump (very similar to tshark, at least until you start messing with filtering out specific packets or searching for certain patterns or anything more complex) come immediately to mind...
#twalberg's suggestion,
netcat -vv -lu -p 6791 worked.