python: add wait-for-emulator command

python/CHANGELOG.md

@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 _At the moment, the project does **not** adhere to [Semantic Versioning](https://semver.org/spec/v2.0.0.html). That is expected to change with version 1.0._
 
+## [0.11.7] - Unreleased
+
+### Added
+
+- built-in functionality of UdpTransport to wait until an emulator comes up, and the
+  related command `trezorctl wait-for-emulator`
+
 ## [0.11.6] - 2019-12-30
 [0.11.6]: https://github.com/trezor/trezor-firmware/compare/python/v0.11.5...python/v0.11.6
 

python/src/trezorlib/cli/trezorctl.py

@@ -19,12 +19,14 @@
 import json
 import os
 import sys
+import time
 
 import click
 
 from .. import coins, log, messages, protobuf, ui
 from ..client import TrezorClient
 from ..transport import enumerate_devices, get_transport
+from ..transport.udp import UdpTransport
 from . import (
     binance,
     btc,
@@ -250,6 +252,28 @@ def usb_reset():
     WebUsbTransport.enumerate(usb_reset=True)
 
 
+@cli.command()
+@click.option("-t", "--timeout", type=float, default=10, help="Timeout in seconds")
+@click.pass_context
+def wait_for_emulator(ctx, timeout):
+    """Wait until Trezor Emulator comes up.
+
+    Tries to connect to emulator and returns when it succeeds.
+    """
+    path = ctx.parent.params.get("path")
+    if path:
+        if not path.startswith("udp:"):
+            raise click.ClickException("You must use UDP path, not {}".format(path))
+        path = path.replace("udp:", "")
+
+    start = time.monotonic()
+    UdpTransport(path).wait_until_ready(timeout)
+    end = time.monotonic()
+
+    if ctx.parent.params.get("verbose"):
+        click.echo("Waited for {:.3f} seconds".format(end - start))
+
+
 #
 # Basic coin functions
 #

python/src/trezorlib/transport/udp.py

@@ -15,6 +15,7 @@
 # If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
 
 import socket
+import time
 from typing import Iterable, Optional, cast
 
 from . import TransportException
@@ -60,7 +61,7 @@ class UdpTransport(ProtocolBasedTransport):
                 return d
             else:
                 raise TransportException(
-                    "No Trezor device found at address {}".format(path)
+                    "No Trezor device found at address {}".format(d.get_path())
                 )
         finally:
             d.close()
@@ -84,6 +85,22 @@ class UdpTransport(ProtocolBasedTransport):
             path = path.replace("{}:".format(cls.PATH_PREFIX), "")
             return cls._try_path(path)
 
+    def wait_until_ready(self, timeout: float = 10) -> None:
+        try:
+            self.open()
+            self.socket.settimeout(0)
+            start = time.monotonic()
+            while True:
+                if self._ping():
+                    break
+                elapsed = time.monotonic() - start
+                if elapsed >= timeout:
+                    raise TransportException("Timed out waiting for connection.")
+
+                time.sleep(0.05)
+        finally:
+            self.close()
+
     def open(self) -> None:
         self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
         self.socket.connect(self.device)