I'm looking for a quick and simple method for properly testing if a given TCP port is open on a remote server, from inside a Shell script.
I've managed to do it with the telnet command, and it works fine when the port is opened, but it doesn't seem to timeout when it's not and just hangs there...
Here's a sample:
l_TELNET=`echo "quit" | telnet $SERVER $PORT | grep "Escape character is"`
if [ "$?" -ne 0 ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fi
I either need a better way, or a way to force telnet to timeout if it doesn't connect in under 8 seconds for example, and return something I can catch in Shell (return code, or string in stdout).
I know of the Perl method, which uses the IO::Socket::INET module and wrote a successful script that tests a port, but would rather like to avoid using Perl if possible.
Note: This is what my server is running (where I need to run this from)
SunOS 5.10 Generic_139556-08 i86pc i386 i86pc
As pointed by B. Rhodes, nc (netcat) will do the job. A more compact way to use it:
nc -z <host> <port>
That way nc will only check if the port is open, exiting with 0 on success, 1 on failure.
For a quick interactive check (with a 5 seconds timeout):
nc -z -v -w5 <host> <port>
It's easy enough to do with the -z and -w TIMEOUT options to nc, but not all systems have nc installed. If you have a recent enough version of bash, this will work:
# Connection successful:
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/80'
$ echo $?
0
# Connection failure prior to the timeout
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/sfsfdfdff.com/80'
bash: sfsfdfdff.com: Name or service not known
bash: /dev/tcp/sfsfdfdff.com/80: Invalid argument
$ echo $?
1
# Connection not established by the timeout
$ timeout 1 bash -c 'cat < /dev/null > /dev/tcp/google.com/81'
$ echo $?
124
What's happening here is that timeout will run the subcommand and kill it if it doesn't exit within the specified timeout (1 second in the above example). In this case bash is the subcommand and uses its special /dev/tcp handling to try and open a connection to the server and port specified. If bash can open the connection within the timeout, cat will just close it immediately (since it's reading from /dev/null) and exit with a status code of 0 which will propagate through bash and then timeout. If bash gets a connection failure prior to the specified timeout, then bash will exit with an exit code of 1 which timeout will also return. And if bash isn't able to establish a connection and the specified timeout expires, then timeout will kill bash and exit with a status of 124.
TOC:
Using bash and timeout
Command
Examples
Using nc
Command
RHEL 6 (nc-1.84)
Installation
Examples
RHEL 7 (nmap-ncat-6.40)
Installation
Examples
Remarks
Using bash and timeout:
Note that timeout should be present with RHEL 6+, or is alternatively found in GNU coreutils 8.22. On MacOS, install it using brew install coreutils and use it as gtimeout.
Command:
$ timeout $TIMEOUT_SECONDS bash -c "</dev/tcp/${HOST}/${PORT}"; echo $?
If parametrizing the host and port, be sure to specify them as ${HOST} and ${PORT} as is above. Do not specify them merely as $HOST and $PORT, i.e. without the braces; it won't work in this case.
Example:
Success:
$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/80"; echo $?
0
Failure:
$ timeout 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
124
If you must preserve the exit status of bash,
$ timeout --preserve-status 2 bash -c "</dev/tcp/canyouseeme.org/81"; echo $?
143
Using nc:
Note that a backward incompatible version of nc gets installed on RHEL 7.
Command:
Note that the command below is unique in that it is identical for both RHEL 6 and 7. It's just the installation and output that are different.
$ nc -w $TIMEOUT_SECONDS -v $HOST $PORT </dev/null; echo $?
RHEL 6 (nc-1.84):
Installation:
$ sudo yum install nc
Examples:
Success:
$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $?
Connection to canyouseeme.org 80 port [tcp/http] succeeded!
0
Failure:
$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $?
nc: connect to canyouseeme.org port 81 (tcp) timed out: Operation now in progress
1
If the hostname maps to multiple IPs, the above failing command will cycle through many or all of them. For example:
$ nc -w 2 -v microsoft.com 81 </dev/null; echo $?
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
nc: connect to microsoft.com port 81 (tcp) timed out: Operation now in progress
1
RHEL 7 (nmap-ncat-6.40):
Installation:
$ sudo yum install nmap-ncat
Examples:
Success:
$ nc -w 2 -v canyouseeme.org 80 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connected to 52.202.215.126:80.
Ncat: 0 bytes sent, 0 bytes received in 0.22 seconds.
0
Failure:
$ nc -w 2 -v canyouseeme.org 81 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connection timed out.
1
If the hostname maps to multiple IPs, the above failing command will cycle through many or all of them. For example:
$ nc -w 2 -v microsoft.com 81 </dev/null; echo $?
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connection to 104.43.195.251 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 23.100.122.175 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 23.96.52.53 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection to 191.239.213.197 failed: Connection timed out.
Ncat: Trying next address...
Ncat: Connection timed out.
1
Remarks:
The -v (--verbose) argument and the echo $? command are of course for illustration only.
With netcat you can check whether a port is open like this:
nc my.example.com 80 < /dev/null
The return value of nc will be success if the TCP port was opened, and failure (typically the return code 1) if it could not make the TCP connection.
Some versions of nc will hang when you try this, because they do not close the sending half of their socket even after receiving the end-of-file from /dev/null. On my own Ubuntu laptop (18.04), the netcat-openbsd version of netcat that I have installed offers a workaround: the -N option is necessary to get an immediate result:
nc -N my.example.com 80 < /dev/null
In Bash using pseudo-device files for TCP/UDP connections is straight forward. Here is the script:
#!/usr/bin/env bash
SERVER=example.com
PORT=80
</dev/tcp/$SERVER/$PORT
if [ "$?" -ne 0 ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fi
Testing:
$ ./test.sh
Connection to example.com on port 80 succeeded
Here is one-liner (Bash syntax):
</dev/tcp/localhost/11211 && echo Port open. || echo Port closed.
Note that some servers can be firewall protected from SYN flood attacks, so you may experience a TCP connection timeout (~75secs). To workaround the timeout issue, try:
timeout 1 bash -c "</dev/tcp/stackoverflow.com/81" && echo Port open. || echo Port closed.
See: How to decrease TCP connect() system call timeout?
I needed a more flexible solution for working on multiple git repositories so I wrote the following sh code based on 1 and 2. You can use your server address instead of gitlab.com and your port in replace of 22.
SERVER=gitlab.com
PORT=22
nc -z -v -w5 $SERVER $PORT
result1=$?
#Do whatever you want
if [ "$result1" != 0 ]; then
echo 'port 22 is closed'
else
echo 'port 22 is open'
fi
check ports using bash
Example
$ ./test_port_bash.sh 192.168.7.7 22
the port 22 is open
Code
HOST=$1
PORT=$2
exec 3> /dev/tcp/${HOST}/${PORT}
if [ $? -eq 0 ];then echo "the port $2 is open";else echo "the port $2 is closed";fi
If you're using ksh or bash they both support IO redirection to/from a socket using the /dev/tcp/IP/PORT construct. In this Korn shell example I am redirecting no-op's (:) std-in from a socket:
W$ python -m SimpleHTTPServer &
[1] 16833
Serving HTTP on 0.0.0.0 port 8000 ...
W$ : </dev/tcp/127.0.0.1/8000
The shell prints an error if the socket is not open:
W$ : </dev/tcp/127.0.0.1/8001
ksh: /dev/tcp/127.0.0.1/8001: cannot open [Connection refused]
You can therefore use this as the test in an if condition:
SERVER=127.0.0.1 PORT=8000
if (: < /dev/tcp/$SERVER/$PORT) 2>/dev/null
then
print succeeded
else
print failed
fi
The no-op is in a subshell so I can throw std-err away if the std-in redirection fails.
I often use /dev/tcp for checking the availability of a resource over HTTP:
W$ print arghhh > grr.html
W$ python -m SimpleHTTPServer &
[1] 16863
Serving HTTP on 0.0.0.0 port 8000 ...
W$ (print -u9 'GET /grr.html HTTP/1.0\n';cat <&9) 9<>/dev/tcp/127.0.0.1/8000
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/2.6.1
Date: Thu, 14 Feb 2013 12:56:29 GMT
Content-type: text/html
Content-Length: 7
Last-Modified: Thu, 14 Feb 2013 12:55:44 GMT
arghhh
W$
This one-liner opens file descriptor 9 for reading from and writing to the socket, prints the HTTP GET to the socket and uses cat to read from the socket.
While an old question, I've just dealt with a variant of it, but none of the solutions here were applicable, so I found another, and am adding it for posterity. Yes, I know the OP said they were aware of this option and it didn't suit them, but for anyone following afterwards it might prove useful.
In my case, I want to test for the availability of a local apt-cacher-ng service from a docker build. That means absolutely nothing can be installed prior to the test. No nc, nmap, expect, telnet or python. perl however is present, along with the core libraries, so I used this:
perl -MIO::Socket::INET -e 'exit(! defined( IO::Socket::INET->new("172.17.42.1:3142")))'
In some cases where tools like curl, telnet, nc o nmap are unavailable you still have a chance with wget
if [[ $(wget -q -t 1 --spider --dns-timeout 3 --connect-timeout 10 host:port; echo $?) -eq 0 ]]; then echo "OK"; else echo "FAIL"; fi
If you want to use nc but don't have a version that support -z, try using --send-only:
nc --send-only <IP> <PORT> </dev/null
and with timeout:
nc -w 1 --send-only <IP> <PORT> </dev/null
and without DNS lookup if it's an IP:
nc -n -w 1 --send-only <IP> <PORT> </dev/null
It returns the codes as the -z based on if it can connect or not.
Building on the most highly voted answer, here is a function to wait for two ports to be open, with a timeout as well. Note the two ports that mus be open, 8890 and 1111, as well as the max_attempts (1 per second).
function wait_for_server_to_boot()
{
echo "Waiting for server to boot up..."
attempts=0
max_attempts=30
while ( nc 127.0.0.1 8890 < /dev/null || nc 127.0.0.1 1111 < /dev/null ) && [[ $attempts < $max_attempts ]] ; do
attempts=$((attempts+1))
sleep 1;
echo "waiting... (${attempts}/${max_attempts})"
done
}
I needed short script which was run in cron and hasn't output. I solve my trouble using nmap
open=`nmap -p $PORT $SERVER | grep "$PORT" | grep open`
if [ -z "$open" ]; then
echo "Connection to $SERVER on port $PORT failed"
exit 1
else
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
fi
To run it You should install nmap because it is not default installed package.
I'm guessing that it's too late for an answer, and this might not be a good one, but here you go...
What about putting it inside of a while loop with a timer on it of some sort. I'm more of a Perl guy than Solaris, but depending on the shell you're using, you should be able to do something like:
TIME = 'date +%s' + 15
while TIME != `date +%s'
do whatever
And then just add a flag in the while loop, so that if it times out before completing, you can cite the timeout as reason for failure.
I suspect that the telnet has a timeout switch as well, but just off the top of my head, I think the above will work.
This uses telnet behind the scenes, and seems to work fine on mac/linux. It doesn't use netcat because of the differences between the versions on linux/mac, and this works with a default mac install.
Example:
$ is_port_open.sh 80 google.com
OPEN
$ is_port_open.sh 8080 google.com
CLOSED
is_port_open.sh
PORT=$1
HOST=$2
TIMEOUT_IN_SEC=${3:-1}
VALUE_IF_OPEN=${4:-"OPEN"}
VALUE_IF_CLOSED=${5:-"CLOSED"}
function eztern()
{
if [ "$1" == "$2" ]
then
echo $3
else
echo $4
fi
}
# cross platform timeout util to support mac mostly
# https://gist.github.com/jaytaylor/6527607
function eztimeout() { perl -e 'alarm shift; exec #ARGV' "$#"; }
function testPort()
{
OPTS=""
# find out if port is open using telnet
# by saving telnet output to temporary file
# and looking for "Escape character" response
# from telnet
FILENAME="/tmp/__port_check_$(uuidgen)"
RESULT=$(eztimeout $TIMEOUT_IN_SEC telnet $HOST $PORT &> $FILENAME; cat $FILENAME | tail -n1)
rm -f $FILENAME;
SUCCESS=$(eztern "$RESULT" "Escape character is '^]'." "$VALUE_IF_OPEN" "$VALUE_IF_CLOSED")
echo "$SUCCESS"
}
testPort
My machine does not support nc or /dev/tcp/$hostname/$port but timeout, so I came back to telnet as follows:
if echo "quit" | timeout 2 telnet $SERVER $PORT 2>&1 | grep -q 'Connected to'; then
echo "Connection to $SERVER on port $PORT succeeded"
exit 0
else
echo "Connection to $SERVER on port $PORT failed"
exit 1
fi
nmap-ncat to test for local port that is not already in use
availabletobindon() {
port="$1"
nc -w 2 -i 1 localhost "$port" 2>&1 | grep -v -q 'Idle timeout expired'
return "$?"
}
Related
I have task to create quite complicated bash script, which at first part is checking the connection to host:port with telnet and- if telnet would fail or would not be installed, try the connection using netcat.
I have problem with loop, where it will skip netcat if telnet would connect to the host and also, if both- telnet and netcat would fail- script would finish with error message.
The script:
#!/bin/bash
echo Type host IP address
read REMOTEHOST
echo Type port number
read REMOTEPORT
TIMEOUT=5
echo quit | timeout --signal=9 5 telnet $REMOTEHOST $REMOTEPORT
if nc -w $TIMEOUT -z $REMOTEHOST $REMOTEPORT; then
echo "I was able to connect to ${REMOTEHOST}:${REMOTEPORT}"
else
echo "Connection to ${REMOTEHOST}:${REMOTEPORT} failed. Exit code from Netcat was ($?)."
fi
You can use the $? variable to get the exit code from the last command.
I found that your original telnet command exits with error code 1 on my system because the escape character is ^]. When I telnet manually I need to hit ctrl-] to enter the telnet prompt, then I can enter 'quit'.
The trick here is you cannot just type ^], you have to type ctrl-v ctrl-]
ctrl-v tells the system to capture the next ctrl character.
The following gives me an exit code of 0, and you can verify by running it manually with echo $? at the command line
-- remember to use ctrl-v ctr-]
$ (echo ^]; echo quit) | timeout --signal=9 5 telnet <REMOTEHOST> <REMOTEPORT>
$ echo $?
Then you can use this in your script:
#!/bin/bash
echo Type host IP address
read REMOTEHOST
echo Type port number
read REMOTEPORT
TIMEOUT=5
(echo ^]; echo quit) | timeout --signal=9 5 telnet $REMOTEHOST $REMOTEPORT > /dev/null 2>&1
TELNET_EXIT_CODE=$?
if [[ $TELNET_EXIT_CODE -ne 0 ]]; then
nc -w $TIMEOUT -z $REMOTEHOST $REMOTEPORT > /dev/null 2>&1
NC_EXIT_CODE=$?
fi
if [[ $TELNET_EXIT_CODE -eq 0 ]] || [[ $NC_EXIT_CODE -eq 0 ]]; then
echo "success"
else
echo "fail"
fi
Tested on Ubuntu 20.04.04, GNU bash version 5.0.17, Telnet version 0.17-41
I am running following command to test port connectivity
curl -v telnet://target ip address:desired port number
When server connects successfully I see output as below:
# curl -v telnet://127.0.0.1:22
* About to connect() to 127.0.0.1 port 22 (#0)
* Trying 127.0.0.1... connected
* Connected to 127.0.0.1 (127.0.0.1) port 22 (#0)
When server doesn't connects successfully I see output as below:
# curl -v telnet://127.0.0.1:22
* About to connect() to 127.0.0.1 port 22 (#0)
* Trying 127.0.0.1...
Now for a given list of servers, I am trying to automate it using bash script.
for element in "${array[#]}"; do
timeout 2s curl -v telnet://"$element":22 >/dev/null 2>&1
if [ $? -eq 0 ]; then
echo "'$element' connected" && break
else
echo "Connection with $element failed."
fi
done
The array has values:
abc001
abc002
abc003
I am always getting output from within else statement
Connection with abc001 failed.
Connection with abc002 failed.
Connection with abc003 failed.
I think it is because the return code is always 124
The error code is 124 for both success and failure
How can I modify my script to work correctly?
You could grep the output for some string indicating success. E.g.,
if timeout 2s curl -v telnet://"$element":22 2>&1 | grep "Connected to"; then
...
else
...
fi
curl has an optional argument --connect-timeout <seconds>. My suggestion would be to revise your curl command to something like:
for element in "${array[#]}"; do
curl -v --connect-timeout 2 telnet://"${element}":22
if [[ $? -eq 0 ]]; then
echo "'${element}' connected"
else
echo "Connection with ${element} failed."
fi
done
A good reference would be the curl man page.
I am using nc command in my Linux box like below to check if a port is listening;
This displays success message:
nc -z 192.168.0.2 9000
This displays 0:
echo $?
I have combined it in a shell script .sh file like below;
#!/bin/sh
nc -z 192.168.0.2 9000
echo $?
This displays 1 instead of expected 0. Again, if I modify my script like below, it works;
#!/bin/sh
echo nc -z 192.168.0.2 9000
echo $?
But here the problem is, it displays success message on one like, then displays 0 in next line. I don't want success message, and I am expecting 0. What is wrong here and how can I fix this?
This small script should do the trick:
#!/bin/bash
SERVER=$1
PORT=$2
nc -z -v -G5 $SERVER $PORT &> /dev/null
result1=$?
#Do whatever you want
if [ "$result1" != 0 ]; then
echo port $PORT is closed on $SERVER
else
echo port $PORT is open on $SERVER
fi
Usage:
./myscript.sh servername portnumber
For example:
./myscript www.google.com 80
www.google.com 80
port 80 is open on www.google.com
Depending on the version of nc you're using, you may need to adjust the -G to -w, so experiment and find which works best for you.
Your script works as expected for me.
(Using nc 0.7.1 and sh 4.4.12)
Both, on command line as well as a script using #!/bin/sh
Just your last version - echo nc -z 192.168.0.2 9000 - does not execute nc at all but just echoes it out. Try replacing nc with anything, e.g. ncc-1701 and you'll see what i mean.
I am trying to write a shell script which takes an IP address and a port number as input and outputs whether the port is open on the host.. My shell script looks like this
#!/bin/bash
name=$(echo exit | telnet $1 $2 | grep "Connected")
if [ "$name" == "" ]
then
echo "Port $2 is not open on $1"
else
echo "Port $2 is open on $1"
fi
It works fine but my output contains 2 lines, something like this:
[root#ip-172-31-8-36 Scripts]# ./test.sh 172.31.35.246 7199
Connection closed by foreign host.
Port 7199 is open on 172.31.35.246
OR
[root#ip-172-31-8-36 Scripts]# ./test.sh 172.31.35.246 7200
telnet: connect to address 172.31.35.246: Connection refused
Port 7200 is not open on 172.31.35.246
I want to suppress the 1st line from the output in both cases.
Any idea how to do it?
Direct telnet's error output to /dev/null:
name=$(echo exit | telnet $1 $2 2>/dev/null | grep "Connected")
The poor-man's nmap in pure bash:
host="127.0.0.1"
for port in {1..1024}
do
echo "" > /dev/tcp/$host/$port && echo "Port $port is open"
done 2>/dev/null
How about using netcat instead?
$ nc -v -z <host> <port>
Connection to <host> <port> port [tcp/https] succeeded!
I am a beginner user of linux, and also quite newbie at ssh and tunnels.
Anyway, my goal is to maintain a ssh tunnel open in background.
In order to do that, I wrote the following batch that I then added into crontab (the batch is automatically processed every 5 minutes during workdays and from 8am to 9pm).
I read in some other thread in stackoverflow that one should use autossh that will ensure the ssh will always be ok through a recurrent check. So did I....
#!/bin/bash
LOGFILE="/root/Tunnel/logBatchRestart.log"
NOW="$(date +%d/%m/%Y' - '%H:%M)" # date & time of log
if ! ps ax | grep ssh | grep tunnelToto &> /dev/null
then
echo "[$NOW] ssh tunnel not running : restarting it" >> $LOGFILE
autossh -f -N -L pppp:tunnelToto:nnnnn nom-prenom#193.xxx.yyy.zzz -p qqqq
if ! ps ax | grep ssh | grep toto &> /dev/null
then
echo "[$NOW] failed starting tunnel" >> $LOGFILE
else
echo "[$NOW] restart successfull" >> $LOGFILE
fi
fi
My problem is that sometimes the tunnel stops working, although every thing looks ok (ps ax | grep ssh > the result shows the two expected tasks : autossh main task and the ssh tunnel itself). I actually know about the problem cause the tunnel is used by a third party software that triggers an error as soon as the tunnel is no more responding.
SO I am wondering how I should improve my batch in order It will be able to check the tunnel and restart it if it happens to be dead. I saw some ideas in there, but it was concluded by the "autossh" hint... which I already use. Thus, I am out of ideas... If any of you have, I'd gladly have a look at them!
Thanks for taking interest in my question, and for your (maybe) suggestions!
Instead of checking the ssh process with ps you can do the following trick
create script, that does the following and add it to your crontab via crontab -e
#!/bin/sh
REMOTEUSER=username
REMOTEHOST=remotehost
SSH_REMOTEPORT=22
SSH_LOCALPORT=10022
TUNNEL_REMOTEPORT=8080
TUNNEL_LOCALPORT=8080
createTunnel() {
/usr/bin/ssh -f -N -L$SSH_LOCALPORT:$REMOTEHOST:SSH_REMOTEPORT -L$TUNNEL_LOCALPORT:$REMOTEHOST:TUNNEL_REMOTEPORT $REMOTEUSER#$REMOTEHOST
if [[ $? -eq 0 ]]; then
echo Tunnel to $REMOTEHOST created successfully
else
echo An error occurred creating a tunnel to $REMOTEHOST RC was $?
fi
}
## Run the 'ls' command remotely. If it returns non-zero, then create a new connection
/usr/bin/ssh -p $SSH_LOCALPORT $REMOTEUSER#localhost ls >/dev/null 2>&1
if [[ $? -ne 0 ]]; then
echo Creating new tunnel connection
createTunnel
fi
In fact, this script will open two ports
port 22 which will be used to check if the tunnel is still alive
port 8080 which is the port you might want to use
Please check and send me further questions via comments
(I add this as an answer since there is not enough room for it un a comment)
Ok, I managed to make the batch run to launch the ssh tunnel (I had to specify my hostname instead of localhost in order it could be triggered) :
#!/bin/bash
LOGFILE="/root/Tunnel/logBatchRedemarrage.log"
NOW="$(date +%d/%m/%Y' - '%H:%M)" # date et heure du log
REMOTEUSER=username
REMOTEHOST=remoteHost
SSH_REMOTEPORT=22
SSH_LOCALPORT=10022
TUNNEL_REMOTEPORT=12081
TUNNEL_SPECIFIC_REMOTE_PORT=22223
TUNNEL_LOCALPORT=8082
createTunnel() {
/usr/bin/ssh -f -N -L$SSH_LOCALPORT:$REMOTEHOST:$SSH_REMOTEPORT -L$TUNNEL_LOCALPORT:$REMOTEHOST:$TUNNEL_REMOTEPORT $REMOTEUSER#193.abc.def.ghi -p $TUNNEL_SPECIFIC_REMOTE_PORT
if [[ $? -eq 0 ]]; then
echo [$NOW] Tunnel to $REMOTEHOST created successfully >> $LOGFILE
else
echo [$NOW] An error occurred creating a tunnel to $REMOTEHOST RC was $? >> $LOGFILE
fi
}
## Run the 'ls' command remotely. If it returns non-zero, then create a new connection
/usr/bin/ssh -p $SSH_LOCALPORT $REMOTEUSER#193.abc.def.ghi ls >/dev/null 2>&1
if [[ $? -ne 0 ]]; then
echo [$NOW] Creating new tunnel connection >> $LOGFILE
createTunnel
fi
However, I got some immediate message (below) when the tunnel is running and when cron tries to lauch the batch again... sounds like it cannot listen to it. Also since I need some time to get a proof , I can't say yet it will successfully restart if the tunnel is out.
Here's the response to the second start of the batch.
bind: Address already in use channel_setup_fwd_listener: cannot listen
to port: 10022 bind: Address already in use
channel_setup_fwd_listener: cannot listen to port: 8082 Could not
request local forwarding.