diff --git a/docs/docker.rst b/docs/docker.rst
--- a/docs/docker.rst
+++ b/docs/docker.rst
@@ -73,3 +73,6 @@
 
     $ java -cp app/swh-graph.jar \
         org.softwareheritage.graph.App data/compressed/g
+
+To specify the port on which the server will run, use the `--port` or `-p` flag
+(default is 5009).
diff --git a/java/server/pom.xml b/java/server/pom.xml
--- a/java/server/pom.xml
+++ b/java/server/pom.xml
@@ -59,6 +59,11 @@
             <artifactId>fastutil</artifactId>
             <version>8.2.2</version>
         </dependency>
+        <dependency>
+            <groupId>com.martiansoftware</groupId>
+            <artifactId>jsap</artifactId>
+            <version>2.1</version>
+        </dependency>
     </dependencies>
 
     <build>
diff --git a/java/server/src/main/java/org/softwareheritage/graph/App.java b/java/server/src/main/java/org/softwareheritage/graph/App.java
--- a/java/server/src/main/java/org/softwareheritage/graph/App.java
+++ b/java/server/src/main/java/org/softwareheritage/graph/App.java
@@ -6,6 +6,13 @@
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.PropertyNamingStrategy;
+import com.martiansoftware.jsap.FlaggedOption;
+import com.martiansoftware.jsap.JSAP;
+import com.martiansoftware.jsap.JSAPException;
+import com.martiansoftware.jsap.JSAPResult;
+import com.martiansoftware.jsap.Parameter;
+import com.martiansoftware.jsap.SimpleJSAP;
+import com.martiansoftware.jsap.UnflaggedOption;
 import io.javalin.Javalin;
 import io.javalin.http.Context;
 import io.javalin.plugin.json.JavalinJackson;
@@ -24,10 +31,32 @@
  */
 
 public class App {
-  public static void main(String[] args) throws IOException {
-    String path = args[0];
-    Graph graph = new Graph(path);
-    Stats stats = new Stats(path);
+  public static void main(String[] args) throws IOException, JSAPException {
+    SimpleJSAP jsap = new SimpleJSAP(
+        App.class.getName(),
+        "Server to load and query a compressed graph representation of Software Heritage archive.",
+        new Parameter[] {
+          new FlaggedOption("port", JSAP.INTEGER_PARSER, "5009", JSAP.NOT_REQUIRED, 'p', "port",
+              "Binding port of the server."),
+          new UnflaggedOption("graphPath", JSAP.STRING_PARSER, JSAP.NO_DEFAULT, JSAP.REQUIRED,
+              JSAP.NOT_GREEDY, "The basename of the compressed graph."),
+        }
+    );
+
+    JSAPResult config = jsap.parse(args);
+    if (jsap.messagePrinted()) {
+      System.exit(1);
+    }
+
+    String graphPath = config.getString("graphPath");
+    int port = config.getInt("port");
+
+    startServer(graphPath, port);
+  }
+
+  private static void startServer(String graphPath, int port) throws IOException {
+    Graph graph = new Graph(graphPath);
+    Stats stats = new Stats(graphPath);
 
     // Clean up on exit
     Runtime.getRuntime().addShutdownHook(new Thread() {
@@ -45,7 +74,7 @@
     objectMapper.setPropertyNamingStrategy(PropertyNamingStrategy.SNAKE_CASE);
     JavalinJackson.configure(objectMapper);
 
-    Javalin app = Javalin.create().start(5009);
+    Javalin app = Javalin.create().start(port);
 
     app.before("/stats/*", ctx -> { checkQueryStrings(ctx, ""); });
     app.before("/leaves/*", ctx -> { checkQueryStrings(ctx, "direction|edges"); });