fix(android.c, CmdEntryPoint.java): fix non-critical EADDRINUSE error

app/src/main/cpp/lorie/android.c

@@ -2,6 +2,7 @@
 #pragma clang diagnostic ignored "-Wmissing-prototypes"
 #pragma ide diagnostic ignored "bugprone-reserved-identifier"
 #pragma ide diagnostic ignored "OCUnusedMacroInspection"
+#pragma ide diagnostic ignored "EndlessLoop"
 #define __USE_GNU
 #ifdef HAVE_DIX_CONFIG_H
 #include <dix-config.h>
@@ -20,6 +21,8 @@
 #include <wchar.h>
 #include <inpututils.h>
 #include <randrstr.h>
+#include <linux/in.h>
+#include <arpa/inet.h>
 #include "renderer.h"
 #include "lorie.h"
 
@@ -518,6 +521,56 @@ Java_com_termux_x11_CmdEntryPoint_connected(__unused JNIEnv *env, __unused jclas
     return conn_fd != -1;
 }
 
+JNIEXPORT void JNICALL
+Java_com_termux_x11_CmdEntryPoint_listenForConnections(JNIEnv *env, jobject thiz, jint port, jbyteArray jbytes) {
+    int server_fd, client, count;
+    struct sockaddr_in address = { .sin_family = AF_INET, .sin_addr = { .s_addr = INADDR_ANY }, .sin_port = htons(port) };
+    int addrlen = sizeof(address);
+    jmethodID sendBroadcast = (*env)->GetMethodID(env, (*env)->GetObjectClass(env, thiz), "sendBroadcast", "()V");
+    jbyte *bytes = (jbyte *)(*env)->GetByteArrayElements(env, jbytes, NULL);
+    size_t size = (*env)->GetArrayLength(env, jbytes);
+    uint8_t buffer[512] = {0};
+
+    // Even in the case if it will fail for some reason everything will work fine
+    // But connection will be delayed a bit
+
+    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
+        log(ERROR, "Socket creation failed: %s", strerror(errno));
+        return;
+    }
+
+    setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &(int){1}, sizeof(int));
+    setsockopt(server_fd, SOL_SOCKET, SO_REUSEPORT, &(int){1}, sizeof(int));
+
+    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
+        log(ERROR, "Socket bind failed: %s", strerror(errno));
+        close(server_fd);
+        return;
+    }
+
+    if (listen(server_fd, 5) < 0) {
+        log(ERROR, "Socket listen failed: %s", strerror(errno));
+        close(server_fd);
+        return;
+    }
+
+    while(1) {
+        if ((client = accept(server_fd, (struct sockaddr *)&address, (socklen_t *)&addrlen)) < 0) {
+            log(ERROR, "Socket accept failed: %s", strerror(errno));
+            continue;
+        }
+
+        if ((count = read(client, buffer, sizeof(buffer))) > 0) {
+            if (!memcmp(buffer, bytes, min(count, size))) {
+                log(DEBUG, "New client connection!\n");
+                (*env)->CallVoidMethod(env, thiz, sendBroadcast);
+            }
+        }
+        close(client);
+        client = -1;
+    }
+}
+
 static inline void checkConnection(JNIEnv* env) {
     int retval, b = 0;
 
@@ -712,6 +765,9 @@ Java_com_termux_x11_LorieView_sendTextEvent(JNIEnv *env, __unused jobject thiz,
         jbyte *str = (*env)->GetByteArrayElements(env, text, NULL);
         char *p = (char*) str;
         mbstate_t state = { 0 };
+        if (!length)
+            return;
+
         log(DEBUG, "Parsing text: %.*s", length, str);
 
         while (*p) {

app/src/main/java/com/termux/x11/CmdEntryPoint.java

@@ -22,15 +22,11 @@
 
 import androidx.annotation.Keep;
 
-import java.io.DataInputStream;
 import java.io.OutputStream;
 import java.io.PrintStream;
 import java.net.ConnectException;
-import java.net.InetAddress;
-import java.net.ServerSocket;
 import java.net.Socket;
 import java.net.URL;
-import java.util.Arrays;
 
 @Keep @SuppressLint({"StaticFieldLeak", "UnsafeDynamicallyLoadedCode"})
 public class CmdEntryPoint extends ICmdEntryInterface.Stub {
@@ -132,36 +128,7 @@ private void sendBroadcastDelayed() {
     }
 
     void spawnListeningThread() {
-        new Thread(() -> { // New thread is needed to avoid android.os.NetworkOnMainThreadException
-            /*
-                The purpose of this function is simple. If the application has not been launched
-                before running termux-x11, the initial sendBroadcast had no effect because no one
-                received the intent. To allow the application to reconnect freely, we will listen on
-                port `PORT` and when receiving a magic phrase, we will send another intent.
-             */
-            Log.e("CmdEntryPoint", "Listening port " + PORT);
-            try (ServerSocket listeningSocket =
-                         new ServerSocket(PORT, 0, InetAddress.getByName("127.0.0.1"))) {
-                listeningSocket.setReuseAddress(true);
-                while(true) {
-                    try (Socket client = listeningSocket.accept()) {
-                        Log.e("CmdEntryPoint", "Somebody connected!");
-                        // We should ensure that it is some
-                        byte[] b = new byte[MAGIC.length];
-                        DataInputStream reader = new DataInputStream(client.getInputStream());
-                        reader.readFully(b);
-                        if (Arrays.equals(MAGIC, b)) {
-                            Log.e("CmdEntryPoint", "New client connection!");
-                            sendBroadcast();
-                        }
-                    } catch (Exception e) {
-                        e.printStackTrace(System.err);
-                    }
-                }
-            } catch (Exception e) {
-                e.printStackTrace(System.err);
-            }
-        }).start();
+        new Thread(() -> listenForConnections(PORT, MAGIC)).start();
     }
 
     public static void requestConnection() {
@@ -215,6 +182,7 @@ public static Context createContext() {
     public native ParcelFileDescriptor getXConnection();
     public native ParcelFileDescriptor getLogcatOutput();
     private static native boolean connected();
+    private native void listenForConnections(int port, byte[] bytes);
 
     static {
         try {