Python scanner for the first free port in a range
$begingroup$
I have a distributed application (YARN), which runs a WebApp.
This application use a default port to start (8008), before I start I need to check if port is in use.
A container may run in the same virtual machine, hence port may be in use.
(Max I have 4 containers in WebApp).
I created the following code which seem to work, but want to see if there are some clean ups/improvements suggested.
def port_in_use(port):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
result = sock.connect_ex(('127.0.0.1', port))
if result == 0:
return True
else:
return False
def start_dashboard():
base_port = os.getenv('DASHBOARD_PORT_ENV_VAR', 8008)
scan_ports = True
attempts = 0
max_attempts = 10
while(scan_ports and attempts <= max_attempts):
if port_in_use(base_port):
base_port += 1
attempts += 1
else:
scan_ports = False
if attempts == max_attempts:
raise IOError('Port in use')
dashboard.configure(port=base_port)
dashboard.launch()
python python-3.x networking socket
edited Mar 23 at 13:52
200_success
131k17156420
asked Mar 23 at 7:09
spicyramenspicyramen
307312
$endgroup$
add a comment |
$begingroup$
I have a distributed application (YARN), which runs a WebApp.
This application use a default port to start (8008), before I start I need to check if port is in use.
A container may run in the same virtual machine, hence port may be in use.
(Max I have 4 containers in WebApp).
I created the following code which seem to work, but want to see if there are some clean ups/improvements suggested.
def port_in_use(port):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
result = sock.connect_ex(('127.0.0.1', port))
if result == 0:
return True
else:
return False
def start_dashboard():
base_port = os.getenv('DASHBOARD_PORT_ENV_VAR', 8008)
scan_ports = True
attempts = 0
max_attempts = 10
while(scan_ports and attempts <= max_attempts):
if port_in_use(base_port):
base_port += 1
attempts += 1
else:
scan_ports = False
if attempts == max_attempts:
raise IOError('Port in use')
dashboard.configure(port=base_port)
dashboard.launch()
python python-3.x networking socket
edited Mar 23 at 13:52
200_success
131k17156420
asked Mar 23 at 7:09
spicyramenspicyramen
307312
$endgroup$
add a comment |
$begingroup$
I have a distributed application (YARN), which runs a WebApp.
This application use a default port to start (8008), before I start I need to check if port is in use.
A container may run in the same virtual machine, hence port may be in use.
(Max I have 4 containers in WebApp).
I created the following code which seem to work, but want to see if there are some clean ups/improvements suggested.
def port_in_use(port):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
result = sock.connect_ex(('127.0.0.1', port))
if result == 0:
return True
else:
return False
def start_dashboard():
base_port = os.getenv('DASHBOARD_PORT_ENV_VAR', 8008)
scan_ports = True
attempts = 0
max_attempts = 10
while(scan_ports and attempts <= max_attempts):
if port_in_use(base_port):
base_port += 1
attempts += 1
else:
scan_ports = False
if attempts == max_attempts:
raise IOError('Port in use')
dashboard.configure(port=base_port)
dashboard.launch()
python python-3.x networking socket
edited Mar 23 at 13:52
200_success
131k17156420
asked Mar 23 at 7:09
spicyramenspicyramen
307312
$endgroup$
I have a distributed application (YARN), which runs a WebApp.
This application use a default port to start (8008), before I start I need to check if port is in use.
A container may run in the same virtual machine, hence port may be in use.
(Max I have 4 containers in WebApp).
I created the following code which seem to work, but want to see if there are some clean ups/improvements suggested.
def port_in_use(port):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
result = sock.connect_ex(('127.0.0.1', port))
if result == 0:
return True
else:
return False
def start_dashboard():
base_port = os.getenv('DASHBOARD_PORT_ENV_VAR', 8008)
scan_ports = True
attempts = 0
max_attempts = 10
while(scan_ports and attempts <= max_attempts):
if port_in_use(base_port):
base_port += 1
attempts += 1
else:
scan_ports = False
if attempts == max_attempts:
raise IOError('Port in use')
dashboard.configure(port=base_port)
dashboard.launch()
python python-3.x networking socket
python python-3.x networking socket
edited Mar 23 at 13:52
200_success
131k17156420
asked Mar 23 at 7:09
spicyramenspicyramen
307312
edited Mar 23 at 13:52
200_success
131k17156420
asked Mar 23 at 7:09
spicyramenspicyramen
307312
edited Mar 23 at 13:52
200_success
131k17156420
edited Mar 23 at 13:52
200_success
131k17156420
edited Mar 23 at 13:52
200_success
131k17156420
131k17156420
asked Mar 23 at 7:09
spicyramenspicyramen
307312
asked Mar 23 at 7:09
spicyramenspicyramen
307312
asked Mar 23 at 7:09
spicyramenspicyramen
307312
307312
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
Your code has some incorrect assumptions.
an application may listen on a specific address/port combination;
127.0.0.1:portcan be available while*:portis not.an application may bind a port without listening. Connects will fail, but so will your own bind.
a firewall or other mechanism can interfere with connections, generating false positives in your scan.
The reliable approach is to bind the port, just as your dashboard will, and then release it.
result = sock.bind(('', port))
sock.close()
You'll need to catch the exception and this is a good opportunity to move the whole thing into a function. That will make the start_dashboard logic cleaner and get rid of boolean loop-terminator scan_ports. Just exit the loop by returning the answer.
def next_free_port( port=1024, max_port=65535 ):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
while port <= max_port:
try:
sock.bind(('', port))
sock.close()
return port
except OSError:
port += 1
raise IOError('no free ports')
def start_dashboard():
# pass optional second parameter "max_port" here, else scan until a free one is found
port = next_free_port( os.getenv('DASHBOARD_PORT_ENV_VAR', 8008) )
dashboard.configure(port=port)
dashboard.launch()
You can use netcat to make ports in-use for testing: nc -l -p 9999 will listen on port 9999; press control-C to end it.
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
$endgroup$
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
1
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
1
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
|
show 1 more comment
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Your code has some incorrect assumptions.
an application may listen on a specific address/port combination;
127.0.0.1:portcan be available while*:portis not.an application may bind a port without listening. Connects will fail, but so will your own bind.
a firewall or other mechanism can interfere with connections, generating false positives in your scan.
The reliable approach is to bind the port, just as your dashboard will, and then release it.
result = sock.bind(('', port))
sock.close()
You'll need to catch the exception and this is a good opportunity to move the whole thing into a function. That will make the start_dashboard logic cleaner and get rid of boolean loop-terminator scan_ports. Just exit the loop by returning the answer.
def next_free_port( port=1024, max_port=65535 ):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
while port <= max_port:
try:
sock.bind(('', port))
sock.close()
return port
except OSError:
port += 1
raise IOError('no free ports')
def start_dashboard():
# pass optional second parameter "max_port" here, else scan until a free one is found
port = next_free_port( os.getenv('DASHBOARD_PORT_ENV_VAR', 8008) )
dashboard.configure(port=port)
dashboard.launch()
You can use netcat to make ports in-use for testing: nc -l -p 9999 will listen on port 9999; press control-C to end it.
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
$endgroup$
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
1
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
1
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
|
show 1 more comment
$begingroup$
Your code has some incorrect assumptions.
an application may listen on a specific address/port combination;
127.0.0.1:portcan be available while*:portis not.an application may bind a port without listening. Connects will fail, but so will your own bind.
a firewall or other mechanism can interfere with connections, generating false positives in your scan.
The reliable approach is to bind the port, just as your dashboard will, and then release it.
result = sock.bind(('', port))
sock.close()
You'll need to catch the exception and this is a good opportunity to move the whole thing into a function. That will make the start_dashboard logic cleaner and get rid of boolean loop-terminator scan_ports. Just exit the loop by returning the answer.
def next_free_port( port=1024, max_port=65535 ):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
while port <= max_port:
try:
sock.bind(('', port))
sock.close()
return port
except OSError:
port += 1
raise IOError('no free ports')
def start_dashboard():
# pass optional second parameter "max_port" here, else scan until a free one is found
port = next_free_port( os.getenv('DASHBOARD_PORT_ENV_VAR', 8008) )
dashboard.configure(port=port)
dashboard.launch()
You can use netcat to make ports in-use for testing: nc -l -p 9999 will listen on port 9999; press control-C to end it.
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
$endgroup$
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
1
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
1
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
|
show 1 more comment
$begingroup$
Your code has some incorrect assumptions.
an application may listen on a specific address/port combination;
127.0.0.1:portcan be available while*:portis not.an application may bind a port without listening. Connects will fail, but so will your own bind.
a firewall or other mechanism can interfere with connections, generating false positives in your scan.
The reliable approach is to bind the port, just as your dashboard will, and then release it.
result = sock.bind(('', port))
sock.close()
You'll need to catch the exception and this is a good opportunity to move the whole thing into a function. That will make the start_dashboard logic cleaner and get rid of boolean loop-terminator scan_ports. Just exit the loop by returning the answer.
def next_free_port( port=1024, max_port=65535 ):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
while port <= max_port:
try:
sock.bind(('', port))
sock.close()
return port
except OSError:
port += 1
raise IOError('no free ports')
def start_dashboard():
# pass optional second parameter "max_port" here, else scan until a free one is found
port = next_free_port( os.getenv('DASHBOARD_PORT_ENV_VAR', 8008) )
dashboard.configure(port=port)
dashboard.launch()
You can use netcat to make ports in-use for testing: nc -l -p 9999 will listen on port 9999; press control-C to end it.
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
$endgroup$
Your code has some incorrect assumptions.
an application may listen on a specific address/port combination;
127.0.0.1:portcan be available while*:portis not.an application may bind a port without listening. Connects will fail, but so will your own bind.
a firewall or other mechanism can interfere with connections, generating false positives in your scan.
The reliable approach is to bind the port, just as your dashboard will, and then release it.
result = sock.bind(('', port))
sock.close()
You'll need to catch the exception and this is a good opportunity to move the whole thing into a function. That will make the start_dashboard logic cleaner and get rid of boolean loop-terminator scan_ports. Just exit the loop by returning the answer.
def next_free_port( port=1024, max_port=65535 ):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
while port <= max_port:
try:
sock.bind(('', port))
sock.close()
return port
except OSError:
port += 1
raise IOError('no free ports')
def start_dashboard():
# pass optional second parameter "max_port" here, else scan until a free one is found
port = next_free_port( os.getenv('DASHBOARD_PORT_ENV_VAR', 8008) )
dashboard.configure(port=port)
dashboard.launch()
You can use netcat to make ports in-use for testing: nc -l -p 9999 will listen on port 9999; press control-C to end it.
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
edited Mar 24 at 7:23
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
answered Mar 23 at 8:49
Oh My GoodnessOh My Goodness
2,004315
2,004315
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
1
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
1
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
|
show 1 more comment
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
1
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
1
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
Thank you for the answer, check is local, so no firewall in place.
$endgroup$
– spicyramen
Mar 23 at 17:42
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
I mean a host firewall, like iptables on Linux.
$endgroup$
– Oh My Goodness
Mar 23 at 19:06
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
$begingroup$
Sounds good, any recommendation for Python style? Thanks
$endgroup$
– spicyramen
Mar 24 at 1:53
1
1
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
$begingroup$
the code can be a little shorter and clearer; see edits for a fleshed-out example.
$endgroup$
– Oh My Goodness
Mar 24 at 6:37
1
1
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
$begingroup$
Thank you! Great sample
$endgroup$
– spicyramen
Mar 24 at 8:37
|
show 1 more comment
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