Accept port range

Accept a range of ports to listen to, so that it does not fail if
another instance of scrcpy is currently starting.

The range can be passed via the command line:

    scrcpy -p 27183:27186
    scrcpy -p 27183  # implicitly 27183:27183, as before

The default is 27183:27199.

Closes #951 <https://github.com/Genymobile/scrcpy/issues/951>

app/meson.build

@@ -96,9 +96,10 @@ conf.set_quoted('PREFIX', get_option('prefix'))
 # directory as the executable)
 conf.set('PORTABLE', get_option('portable'))
 
-# the default client TCP port for the "adb reverse" tunnel
+# the default client TCP port range for the "adb reverse" tunnel
 # overridden by option --port
-conf.set('DEFAULT_LOCAL_PORT', '27183')
+conf.set('DEFAULT_LOCAL_PORT_RANGE_FIRST', '27183')
+conf.set('DEFAULT_LOCAL_PORT_RANGE_LAST', '27199')
 
 # the default max video size for both dimensions, in pixels
 # overridden by option --max-size

app/scrcpy.1

@@ -60,10 +60,10 @@ Disable device control (mirror the device in read\-only).
 Do not display device (only when screen recording is enabled).
 
 .TP
-.BI "\-p, \-\-port " port
-Set the TCP port the client listens on.
+.BI "\-p, \-\-port " port[:port]
+Set the TCP port (range) used by the client to listen.
 
-Default is 27183.
+Default is 27183:27199.
 
 .TP
 .B \-\-prefer\-text

app/src/cli.c

@@ -58,9 +58,9 @@ scrcpy_print_usage(const char *arg0) {
         "        Do not display device (only when screen recording is\n"
         "        enabled).\n"
         "\n"
-        "    -p, --port port\n"
-        "        Set the TCP port the client listens on.\n"
-        "        Default is %d.\n"
+        "    -p, --port port[:port]\n"
+        "        Set the TCP port (range) used by the client to listen.\n"
+        "        Default is %d:%d.\n"
         "\n"
         "    --prefer-text\n"
         "        Inject alpha characters and space as text events instead of\n"
@@ -193,7 +193,7 @@ scrcpy_print_usage(const char *arg0) {
         arg0,
         DEFAULT_BIT_RATE,
         DEFAULT_MAX_SIZE, DEFAULT_MAX_SIZE ? "" : " (unlimited)",
-        DEFAULT_LOCAL_PORT);
+        DEFAULT_LOCAL_PORT_RANGE_FIRST, DEFAULT_LOCAL_PORT_RANGE_LAST);
 }
 
 static bool
@@ -221,6 +221,27 @@ parse_integer_arg(const char *s, long *out, bool accept_suffix, long min,
     return true;
 }
 
+static size_t
+parse_integers_arg(const char *s, size_t max_items, long *out, long min,
+                   long max, const char *name) {
+    size_t count = parse_integers(s, ':', max_items, out);
+    if (!count) {
+        LOGE("Could not parse %s: %s", name, s);
+        return 0;
+    }
+
+    for (size_t i = 0; i < count; ++i) {
+        long value = out[i];
+        if (value < min || value > max) {
+            LOGE("Could not parse %s: value (%ld) out-of-range (%ld; %ld)",
+                 name, value, min, max);
+            return 0;
+        }
+    }
+
+    return count;
+}
+
 static bool
 parse_bit_rate(const char *s, uint32_t *bit_rate) {
     long value;
@@ -286,14 +307,30 @@ parse_window_dimension(const char *s, uint16_t *dimension) {
 }
 
 static bool
-parse_port(const char *s, uint16_t *port) {
-    long value;
-    bool ok = parse_integer_arg(s, &value, false, 0, 0xFFFF, "port");
-    if (!ok) {
+parse_port_range(const char *s, struct port_range *port_range) {
+    long values[2];
+    size_t count = parse_integers_arg(s, 2, values, 0, 0xFFFF, "port");
+    if (!count) {
         return false;
     }
 
-    *port = (uint16_t) value;
+    uint16_t v0 = (uint16_t) values[0];
+    if (count == 1) {
+        port_range->first = v0;
+        port_range->last = v0;
+        return true;
+    }
+
+    assert(count == 2);
+    uint16_t v1 = (uint16_t) values[1];
+    if (v0 < v1) {
+        port_range->first = v0;
+        port_range->last = v1;
+    } else {
+        port_range->first = v1;
+        port_range->last = v0;
+    }
+
     return true;
 }
 
@@ -424,7 +461,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
                 opts->display = false;
                 break;
             case 'p':
-                if (!parse_port(optarg, &opts->port)) {
+                if (!parse_port_range(optarg, &opts->port_range)) {
                     return false;
                 }
                 break;

app/src/common.h

@@ -27,4 +27,9 @@ struct position {
     struct point point;
 };
 
+struct port_range {
+    uint16_t first;
+    uint16_t last;
+};
+
 #endif

app/src/control_msg.c

@@ -75,8 +75,6 @@ control_msg_serialize(const struct control_msg *msg, unsigned char *buf) {
             buf[1] = msg->set_screen_power_mode.mode;
             return 2;
         case CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON:
-            buf[1] = msg->back_or_screen_on.action;
-            return 2;
         case CONTROL_MSG_TYPE_EXPAND_NOTIFICATION_PANEL:
         case CONTROL_MSG_TYPE_COLLAPSE_NOTIFICATION_PANEL:
         case CONTROL_MSG_TYPE_GET_CLIPBOARD:

app/src/control_msg.h

@@ -66,9 +66,6 @@ struct control_msg {
         struct {
             enum screen_power_mode mode;
         } set_screen_power_mode;
-        struct {
-            enum android_keyevent_action action;
-        } back_or_screen_on;
     };
 };
 

app/src/input_manager.c

@@ -99,14 +99,9 @@ action_menu(struct controller *controller, int actions) {
 
 // turn the screen on if it was off, press BACK otherwise
 static void
-press_back_or_turn_screen_on(struct controller *controller, int action) {
-    assert(action == ACTION_DOWN || action == ACTION_UP);
-
+press_back_or_turn_screen_on(struct controller *controller) {
     struct control_msg msg;
     msg.type = CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON;
-    msg.back_or_screen_on.action = action == ACTION_DOWN
-                                 ? AKEY_EVENT_ACTION_DOWN
-                                 : AKEY_EVENT_ACTION_UP;
 
     if (!controller_push_msg(controller, &msg)) {
         LOGW("Could not request 'press back or turn screen on'");
@@ -526,36 +521,31 @@ input_manager_process_mouse_button(struct input_manager *im,
         // simulated from touch events, so it's a duplicate
         return;
     }
-
-    // double-click on black borders resize to fit the device screen
-    if (event->type == SDL_MOUSEBUTTONDOWN
-            && event->button == SDL_BUTTON_LEFT
-            && event->clicks == 2) {
-        bool outside = is_outside_device_screen(im, event->x, event->y);
-        if (outside) {
-            screen_resize_to_fit(im->screen);
+    if (event->type == SDL_MOUSEBUTTONDOWN) {
+        if (control && event->button == SDL_BUTTON_RIGHT) {
+            press_back_or_turn_screen_on(im->controller);
             return;
         }
+        if (control && event->button == SDL_BUTTON_MIDDLE) {
+            action_home(im->controller, ACTION_DOWN | ACTION_UP);
+            return;
+        }
+        // double-click on black borders resize to fit the device screen
+        if (event->button == SDL_BUTTON_LEFT && event->clicks == 2) {
+            bool outside =
+                is_outside_device_screen(im, event->x, event->y);
+            if (outside) {
+                screen_resize_to_fit(im->screen);
+                return;
+            }
+        }
+        // otherwise, send the click event to the device
     }
 
     if (!control) {
         return;
     }
 
-    if (event->button == SDL_BUTTON_MIDDLE) {
-        int action = event->type == SDL_MOUSEBUTTONDOWN ? ACTION_DOWN
-                                                        : ACTION_UP;
-        action_home(im->controller, action);
-        return;
-    }
-
-    if (event->button == SDL_BUTTON_RIGHT) {
-        int action = event->type == SDL_MOUSEBUTTONDOWN ? ACTION_DOWN
-                                                        : ACTION_UP;
-        press_back_or_turn_screen_on(im->controller, action);
-        return;
-    }
-
     struct control_msg msg;
     if (convert_mouse_button(event, im->screen, &msg)) {
         if (!controller_push_msg(im->controller, &msg)) {

app/src/scrcpy.c

@@ -280,7 +280,7 @@ scrcpy(const struct scrcpy_options *options) {
     bool record = !!options->record_filename;
     struct server_params params = {
         .crop = options->crop,
-        .local_port = options->port,
+        .port_range = options->port_range,
         .max_size = options->max_size,
         .bit_rate = options->bit_rate,
         .max_fps = options->max_fps,

app/src/scrcpy.h

@@ -5,6 +5,7 @@
 #include <stdint.h>
 
 #include "config.h"
+#include "common.h"
 #include "input_manager.h"
 #include "recorder.h"
 
@@ -15,7 +16,7 @@ struct scrcpy_options {
     const char *window_title;
     const char *push_target;
     enum recorder_format record_format;
-    uint16_t port;
+    struct port_range port_range;
     uint16_t max_size;
     uint32_t bit_rate;
     uint16_t max_fps;
@@ -41,7 +42,10 @@ struct scrcpy_options {
     .window_title = NULL, \
     .push_target = NULL, \
     .record_format = RECORDER_FORMAT_AUTO, \
-    .port = DEFAULT_LOCAL_PORT, \
+    .port_range = { \
+        .first = DEFAULT_LOCAL_PORT_RANGE_FIRST, \
+        .last = DEFAULT_LOCAL_PORT_RANGE_LAST, \
+    }, \
     .max_size = DEFAULT_MAX_SIZE, \
     .bit_rate = DEFAULT_BIT_RATE, \
     .max_fps = 0, \

app/src/server.c

@@ -126,17 +126,6 @@ disable_tunnel_forward(const char *serial, uint16_t local_port) {
     return process_check_success(process, "adb forward --remove");
 }
 
-static bool
-enable_tunnel(struct server *server) {
-    if (enable_tunnel_reverse(server->serial, server->local_port)) {
-        return true;
-    }
-
-    LOGW("'adb reverse' failed, fallback to 'adb forward'");
-    server->tunnel_forward = true;
-    return enable_tunnel_forward(server->serial, server->local_port);
-}
-
 static bool
 disable_tunnel(struct server *server) {
     if (server->tunnel_forward) {
@@ -145,6 +134,100 @@ disable_tunnel(struct server *server) {
     return disable_tunnel_reverse(server->serial);
 }
 
+static socket_t
+listen_on_port(uint16_t port) {
+#define IPV4_LOCALHOST 0x7F000001
+    return net_listen(IPV4_LOCALHOST, port, 1);
+}
+
+static bool
+enable_tunnel_reverse_any_port(struct server *server,
+                               struct port_range port_range) {
+    uint16_t port = port_range.first;
+    for (;;) {
+        if (!enable_tunnel_reverse(server->serial, port)) {
+            // the command itself failed, it will fail on any port
+            return false;
+        }
+
+        // At the application level, the device part is "the server" because it
+        // serves video stream and control. However, at the network level, the
+        // client listens and the server connects to the client. That way, the
+        // client can listen before starting the server app, so there is no
+        // need to try to connect until the server socket is listening on the
+        // device.
+        server->server_socket = listen_on_port(port);
+        if (server->server_socket != INVALID_SOCKET) {
+            // success
+            server->local_port = port;
+            return true;
+        }
+
+        // failure, disable tunnel and try another port
+        if (!disable_tunnel_reverse(server->serial)) {
+            LOGW("Could not remove reverse tunnel on port %" PRIu16, port);
+        }
+
+        // check before incrementing to avoid overflow on port 65535
+        if (port < port_range.last) {
+            LOGW("Could not listen on port %" PRIu16", retrying on %" PRIu16,
+                 port, port + 1);
+            port++;
+            continue;
+        }
+
+        if (port_range.first == port_range.last) {
+            LOGE("Could not listen on port %" PRIu16, port_range.first);
+        } else {
+            LOGE("Could not listen on any port in range %" PRIu16 ":%" PRIu16,
+                 port_range.first, port_range.last);
+        }
+        return false;
+    }
+}
+
+static bool
+enable_tunnel_forward_any_port(struct server *server,
+                               struct port_range port_range) {
+    server->tunnel_forward = true;
+    uint16_t port = port_range.first;
+    for (;;) {
+        if (enable_tunnel_forward(server->serial, port)) {
+            // success
+            server->local_port = port;
+            return true;
+        }
+
+        if (port < port_range.last) {
+            LOGW("Could not forward port %" PRIu16", retrying on %" PRIu16,
+                 port, port + 1);
+            port++;
+            continue;
+        }
+
+        if (port_range.first == port_range.last) {
+            LOGE("Could not forward port %" PRIu16, port_range.first);
+        } else {
+            LOGE("Could not forward any port in range %" PRIu16 ":%" PRIu16,
+                 port_range.first, port_range.last);
+        }
+        return false;
+    }
+}
+
+static bool
+enable_tunnel_any_port(struct server *server, struct port_range port_range) {
+    if (enable_tunnel_reverse_any_port(server, port_range)) {
+        return true;
+    }
+
+    // if "adb reverse" does not work (e.g. over "adb connect"), it fallbacks to
+    // "adb forward", so the app socket is the client
+
+    LOGW("'adb reverse' failed, fallback to 'adb forward'");
+    return enable_tunnel_forward_any_port(server, port_range);
+}
+
 static process_t
 execute_server(struct server *server, const struct server_params *params) {
     char max_size_string[6];
@@ -187,13 +270,6 @@ execute_server(struct server *server, const struct server_params *params) {
     return adb_execute(server->serial, cmd, sizeof(cmd) / sizeof(cmd[0]));
 }
 
-#define IPV4_LOCALHOST 0x7F000001
-
-static socket_t
-listen_on_port(uint16_t port) {
-    return net_listen(IPV4_LOCALHOST, port, 1);
-}
-
 static socket_t
 connect_and_read_byte(uint16_t port) {
     socket_t socket = net_connect(IPV4_LOCALHOST, port);
@@ -247,7 +323,7 @@ server_init(struct server *server) {
 bool
 server_start(struct server *server, const char *serial,
              const struct server_params *params) {
-    server->local_port = params->local_port;
+    server->port_range = params->port_range;
 
     if (serial) {
         server->serial = SDL_strdup(serial);
@@ -261,30 +337,11 @@ server_start(struct server *server, const char *serial,
         return false;
     }
 
-    if (!enable_tunnel(server)) {
+    if (!enable_tunnel_any_port(server, params->port_range)) {
         SDL_free(server->serial);
         return false;
     }
 
-    // if "adb reverse" does not work (e.g. over "adb connect"), it fallbacks to
-    // "adb forward", so the app socket is the client
-    if (!server->tunnel_forward) {
-        // At the application level, the device part is "the server" because it
-        // serves video stream and control. However, at the network level, the
-        // client listens and the server connects to the client. That way, the
-        // client can listen before starting the server app, so there is no
-        // need to try to connect until the server socket is listening on the
-        // device.
-
-        server->server_socket = listen_on_port(params->local_port);
-        if (server->server_socket == INVALID_SOCKET) {
-            LOGE("Could not listen on port %" PRIu16, params->local_port);
-            disable_tunnel(server);
-            SDL_free(server->serial);
-            return false;
-        }
-    }
-
     // server will connect to our server socket
     server->process = execute_server(server, params);
 

app/src/server.h

@@ -6,6 +6,7 @@
 
 #include "config.h"
 #include "command.h"
+#include "common.h"
 #include "util/net.h"
 
 struct server {
@@ -14,25 +15,30 @@ struct server {
     socket_t server_socket; // only used if !tunnel_forward
     socket_t video_socket;
     socket_t control_socket;
-    uint16_t local_port;
+    struct port_range port_range;
+    uint16_t local_port; // selected from port_range
     bool tunnel_enabled;
     bool tunnel_forward; // use "adb forward" instead of "adb reverse"
 };
 
-#define SERVER_INITIALIZER {          \
-    .serial = NULL,                   \
-    .process = PROCESS_NONE,          \
-    .server_socket = INVALID_SOCKET,  \
-    .video_socket = INVALID_SOCKET,   \
+#define SERVER_INITIALIZER { \
+    .serial = NULL, \
+    .process = PROCESS_NONE, \
+    .server_socket = INVALID_SOCKET, \
+    .video_socket = INVALID_SOCKET, \
     .control_socket = INVALID_SOCKET, \
-    .local_port = 0,                  \
-    .tunnel_enabled = false,          \
-    .tunnel_forward = false,          \
+    .port_range = { \
+        .first = 0, \
+        .last = 0, \
+    }, \
+    .local_port = 0, \
+    .tunnel_enabled = false, \
+    .tunnel_forward = false, \
 }
 
 struct server_params {
     const char *crop;
-    uint16_t local_port;
+    struct port_range port_range;
     uint16_t max_size;
     uint32_t bit_rate;
     uint16_t max_fps;

app/src/util/str_util.c

@@ -81,6 +81,35 @@ parse_integer(const char *s, long *out) {
     return true;
 }
 
+size_t
+parse_integers(const char *s, const char sep, size_t max_items, long *out) {
+    size_t count = 0;
+    char *endptr;
+    do {
+        errno = 0;
+        long value = strtol(s, &endptr, 0);
+        if (errno == ERANGE) {
+            return 0;
+        }
+
+        if (endptr == s || (*endptr != sep && *endptr != '\0')) {
+            return 0;
+        }
+
+        out[count++] = value;
+        if (*endptr == sep) {
+            if (count >= max_items) {
+                // max items already reached, could not accept a new item
+                return 0;
+            }
+            // parse the next token during the next iteration
+            s = endptr + 1;
+        }
+    } while (*endptr != '\0');
+
+    return count;
+}
+
 bool
 parse_integer_with_suffix(const char *s, long *out) {
     char *endptr;

app/src/util/str_util.h

@@ -31,6 +31,11 @@ strquote(const char *src);
 bool
 parse_integer(const char *s, long *out);
 
+// parse s as integers separated by sep (for example '1234:2000')
+// returns the number of integers on success, 0 on failure
+size_t
+parse_integers(const char *s, const char sep, size_t max_items, long *out);
+
 // parse s as an integer into value
 // like parse_integer(), but accept 'k'/'K' (x1000) and 'm'/'M' (x1000000) as
 // suffix

app/tests/test_cli.c

@@ -50,7 +50,7 @@ static void test_options(void) {
         "--max-size", "1024",
         // "--no-control" is not compatible with "--turn-screen-off"
         // "--no-display" is not compatible with "--fulscreen"
-        "--port", "1234",
+        "--port", "1234:1236",
         "--push-target", "/sdcard/Movies",
         "--record", "file",
         "--record-format", "mkv",
@@ -78,7 +78,8 @@ static void test_options(void) {
     assert(opts->fullscreen);
     assert(opts->max_fps == 30);
     assert(opts->max_size == 1024);
-    assert(opts->port == 1234);
+    assert(opts->port_range.first == 1234);
+    assert(opts->port_range.last == 1236);
     assert(!strcmp(opts->push_target, "/sdcard/Movies"));
     assert(!strcmp(opts->record_filename, "file"));
     assert(opts->record_format == RECORDER_FORMAT_MKV);

app/tests/test_control_msg_serialize.c

@@ -140,18 +140,14 @@ static void test_serialize_inject_scroll_event(void) {
 static void test_serialize_back_or_screen_on(void) {
     struct control_msg msg = {
         .type = CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON,
-        .back_or_screen_on = {
-            .action = AKEY_EVENT_ACTION_UP,
-        },
     };
 
     unsigned char buf[CONTROL_MSG_SERIALIZED_MAX_SIZE];
     int size = control_msg_serialize(&msg, buf);
-    assert(size == 2);
+    assert(size == 1);
 
     const unsigned char expected[] = {
         CONTROL_MSG_TYPE_BACK_OR_SCREEN_ON,
-        AKEY_EVENT_ACTION_UP,
     };
     assert(!memcmp(buf, expected, sizeof(expected)));
 }

app/tests/test_strutil.c

@@ -187,6 +187,55 @@ static void test_parse_integer(void) {
     assert(!ok); // out-of-range
 }
 
+static void test_parse_integers(void) {
+    long values[5];
+
+    size_t count = parse_integers("1234", ':', 5, values);
+    assert(count == 1);
+    assert(values[0] == 1234);
+
+    count = parse_integers("1234:5678", ':', 5, values);
+    assert(count == 2);
+    assert(values[0] == 1234);
+    assert(values[1] == 5678);
+
+    count = parse_integers("1234:5678", ':', 2, values);
+    assert(count == 2);
+    assert(values[0] == 1234);
+    assert(values[1] == 5678);
+
+    count = parse_integers("1234:-5678", ':', 2, values);
+    assert(count == 2);
+    assert(values[0] == 1234);
+    assert(values[1] == -5678);
+
+    count = parse_integers("1:2:3:4:5", ':', 5, values);
+    assert(count == 5);
+    assert(values[0] == 1);
+    assert(values[1] == 2);
+    assert(values[2] == 3);
+    assert(values[3] == 4);
+    assert(values[4] == 5);
+
+    count = parse_integers("1234:5678", ':', 1, values);
+    assert(count == 0); // max_items == 1
+
+    count = parse_integers("1:2:3:4:5", ':', 3, values);
+    assert(count == 0); // max_items == 3
+
+    count = parse_integers(":1234", ':', 5, values);
+    assert(count == 0); // invalid
+
+    count = parse_integers("1234:", ':', 5, values);
+    assert(count == 0); // invalid
+
+    count = parse_integers("1234:", ':', 1, values);
+    assert(count == 0); // invalid, even when max_items == 1
+
+    count = parse_integers("1234::5678", ':', 5, values);
+    assert(count == 0); // invalid
+}
+
 static void test_parse_integer_with_suffix(void) {
     long value;
     bool ok = parse_integer_with_suffix("1234", &value);
@@ -249,6 +298,7 @@ int main(void) {
     test_strquote();
     test_utf8_truncate();
     test_parse_integer();
+    test_parse_integers();
     test_parse_integer_with_suffix();
     return 0;
 }

server/src/main/java/com/genymobile/scrcpy/ControlMessage.java

@@ -85,13 +85,6 @@ public final class ControlMessage {
         return msg;
     }
 
-    public static ControlMessage createBackOrScreenOn(int action) {
-        ControlMessage msg = new ControlMessage();
-        msg.type = TYPE_BACK_OR_SCREEN_ON;
-        msg.action = action;
-        return msg;
-    }
-
     public static ControlMessage createEmpty(int type) {
         ControlMessage msg = new ControlMessage();
         msg.type = type;

server/src/main/java/com/genymobile/scrcpy/ControlMessageReader.java

@@ -13,7 +13,6 @@ public class ControlMessageReader {
     private static final int INJECT_TOUCH_EVENT_PAYLOAD_LENGTH = 21;
     private static final int INJECT_SCROLL_EVENT_PAYLOAD_LENGTH = 20;
     private static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
-    private static final int BACK_OR_SCREEN_ON_PAYLOAD_LENGTH = 1;
 
     public static final int TEXT_MAX_LENGTH = 300;
     public static final int CLIPBOARD_TEXT_MAX_LENGTH = 4093;
@@ -74,8 +73,6 @@ public class ControlMessageReader {
                 msg = parseSetScreenPowerMode();
                 break;
             case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
-                msg = parseBackOrScreenOn();
-                break;
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
             case ControlMessage.TYPE_COLLAPSE_NOTIFICATION_PANEL:
             case ControlMessage.TYPE_GET_CLIPBOARD:
@@ -167,14 +164,6 @@ public class ControlMessageReader {
         return ControlMessage.createSetScreenPowerMode(mode);
     }
 
-    private ControlMessage parseBackOrScreenOn() {
-        if (buffer.remaining() < BACK_OR_SCREEN_ON_PAYLOAD_LENGTH) {
-            return null;
-        }
-        int action = toUnsigned(buffer.get());
-        return ControlMessage.createBackOrScreenOn(action);
-    }
-
     private static Position readPosition(ByteBuffer buffer) {
         int x = buffer.getInt();
         int y = buffer.getInt();

server/src/main/java/com/genymobile/scrcpy/Controller.java

@@ -26,9 +26,6 @@ public class Controller {
     private final MotionEvent.PointerProperties[] pointerProperties = new MotionEvent.PointerProperties[PointersState.MAX_POINTERS];
     private final MotionEvent.PointerCoords[] pointerCoords = new MotionEvent.PointerCoords[PointersState.MAX_POINTERS];
 
-    private boolean backPressed;
-    private boolean powerPressed;
-
     public Controller(Device device, DesktopConnection connection) {
         this.device = device;
         this.connection = connection;
@@ -91,7 +88,7 @@ public class Controller {
                 injectScroll(msg.getPosition(), msg.getHScroll(), msg.getVScroll());
                 break;
             case ControlMessage.TYPE_BACK_OR_SCREEN_ON:
-                pressBackOrTurnScreenOn(msg.getAction());
+                pressBackOrTurnScreenOn();
                 break;
             case ControlMessage.TYPE_EXPAND_NOTIFICATION_PANEL:
                 device.expandNotificationPanel();
@@ -226,33 +223,8 @@ public class Controller {
         return device.injectInputEvent(event, InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);
     }
 
-    private boolean pressBackOrTurnScreenOn(int action) {
-        int keycode = -1;
-        if (action == KeyEvent.ACTION_UP) {
-            // if BACK or POWER were pressed, this action is the corresponding release event (regardless of the screen state)
-            if (backPressed) {
-                keycode = KeyEvent.KEYCODE_BACK;
-                backPressed = false;
-            } else if (powerPressed) {
-                keycode = KeyEvent.KEYCODE_POWER;
-                powerPressed = false;
-            }
-        }
-
-        if (keycode == -1) {
-            keycode = device.isScreenOn() ? KeyEvent.KEYCODE_BACK : KeyEvent.KEYCODE_POWER;
-        }
-
-        if (action == KeyEvent.ACTION_DOWN) {
-            if (keycode == KeyEvent.KEYCODE_BACK) {
-                backPressed = true;
-                powerPressed = false;
-            } else {
-                backPressed = false;
-                powerPressed = true;
-            }
-        }
-
-        return injectKeyEvent(action, keycode, 0, 0);
+    private boolean pressBackOrTurnScreenOn() {
+        int keycode = device.isScreenOn() ? KeyEvent.KEYCODE_BACK : KeyEvent.KEYCODE_POWER;
+        return injectKeycode(keycode);
     }
 }

server/src/test/java/com/genymobile/scrcpy/ControlMessageReaderTest.java

@@ -145,7 +145,6 @@ public class ControlMessageReaderTest {
         ByteArrayOutputStream bos = new ByteArrayOutputStream();
         DataOutputStream dos = new DataOutputStream(bos);
         dos.writeByte(ControlMessage.TYPE_BACK_OR_SCREEN_ON);
-        dos.writeByte(KeyEvent.ACTION_UP);
 
         byte[] packet = bos.toByteArray();
 
@@ -153,7 +152,6 @@ public class ControlMessageReaderTest {
         ControlMessage event = reader.next();
 
         Assert.assertEquals(ControlMessage.TYPE_BACK_OR_SCREEN_ON, event.getType());
-        Assert.assertEquals(KeyEvent.ACTION_UP, event.getAction());
     }
 
     @Test