How to find available ports in Java- Baeldung

Jiedao jdon 2021-05-04 18:55:11
available ports java- java baeldung

In this quick tutorial , We'll look at how to check for specific port States and how to use automatically assigned port States . We'll look at how to use ordinary Java and Spring The framework does this . We'll also look at some other server implementations , For example, embedded Tomcat and Jetty.


pure Java

try (ServerSocket serverSocket = new ServerSocket(0)) {
} catch (IOException e) {
    fail("Port is not available");



Spring The framework contains a SocketUtils class , We can use it to find available free ports . Its internal implementation uses ServerSocket class , As shown in the previous example :

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



Server jettyServer = new Server();
ServerConnector serverConnector = new ServerConnector(jettyServer);
try {
} catch (Exception e) {
    fail("Failed to start Jetty server");
} finally {



Tomcat It's another popular one Java Embedded Server , It works in a slightly different way . We can go through Tomcat Class setPort Method to specify an explicit port number . If the port number we provide is zero , be Tomcat A free port will be automatically assigned . however , If we don't set any port numbers , be Tomcat Will use its default port 8080. Please note that , Default Tomcat The port may be occupied by other applications :

Tomcat tomcatServer = new Tomcat();
try {
} catch (LifecycleException e) {
    fail("Failed to start Tomcat server");
} finally {


本文为[Jiedao jdon]所创,转载请带上原文链接,感谢

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