how do i get free ports in the specific range in python

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')

Suggestion : 2

Last Updated : 27 Jul, 2020

To use socket module ,we have to import it :

 import socket

To create a new object of socket socket() is used. The syntax of socket() function is:

 newSocket = socket.socket(socket_family, socket_type)

socket_family is ip address of version 4 or 6.By default it takes as IPV4.

AF_INET
for socket family of address version 4

AF_INET6
for socket family of address version 6

To Return a string containing the hostname of the machine where the Python interpreter is currently executing. we can use :

 socket.gethostname()

If hostname is in IPV6 Following method is used Translate a host name to IPv4 address format. The IPv4 address is returned as a string, such as ‘10.120.30.2’. If the host name is an IPv4 address itself it is returned unchanged.

 socket.gethostbyname(hostname)

Suggestion : 3

Last modified: July 8, 2021

1._

try (ServerSocket serverSocket = new ServerSocket(FREE_PORT_NUMBER)) {
   assertThat(serverSocket).isNotNull();
   assertThat(serverSocket.getLocalPort()).isEqualTo(FREE_PORT_NUMBER);
} catch (IOException e) {
   fail("Port is not available");
}

In case we use a specific port twice, or it's already occupied by another application, the ServerSocket constructor will throw an IOException:

try (ServerSocket serverSocket = new ServerSocket(FREE_PORT_NUMBER)) {
   new ServerSocket(FREE_PORT_NUMBER);
   fail("Same port cannot be used twice");
} catch (IOException e) {
   assertThat(e).hasMessageContaining("Address already in use");
}

Let's now check how we can make use of the thrown IOException, to create a server socket using the first free port from a given range of port numbers:

for (int port: FREE_PORT_RANGE) {
   try (ServerSocket serverSocket = new ServerSocket(port)) {
      assertThat(serverSocket).isNotNull();
      assertThat(serverSocket.getLocalPort()).isEqualTo(port);
      return;
   } catch (IOException e) {
      assertThat(e).hasMessageContaining("Address already in use");
   }
}
fail("No free port in the range found");

5._

int port = SocketUtils.findAvailableTcpPort();
try (ServerSocket serverSocket = new ServerSocket(port)) {
   assertThat(serverSocket).isNotNull();
   assertThat(serverSocket.getLocalPort()).isEqualTo(port);
} catch (IOException e) {
   fail("Port is not available");
}

Jetty is a very popular embedded server for Java applications. It will automatically allocate a free port for us unless we set it explicitly via the setPort method of the ServerConnector class:

Server jettyServer = new Server();
ServerConnector serverConnector = new ServerConnector(jettyServer);
jettyServer.addConnector(serverConnector);
try {
   jettyServer.start();
   assertThat(serverConnector.getLocalPort()).isGreaterThan(0);
} catch (Exception e) {
   fail("Failed to start Jetty server");
} finally {
   jettyServer.stop();
   jettyServer.destroy();
}