Update iOS RPC README (#2847)

apps/ios_rpc/README.md

@@ -4,12 +4,34 @@ This folder contains iOS RPC app that allows us to launch an rpc server on a iOS
 and connect to it through python script and do testing on the python side as normal TVM RPC.
 You will need XCode and an iOS device to use this.
 
+## RPC proxy
+Start the RPC proxy by running in a terminal:
+
+    python -m tvm.exec.rpc_proxy
+
+On success, you should see something like this:
+
+    INFO:root:RPCProxy: client port bind to 0.0.0.0:9090
+    INFO:root:RPCProxy: Websock port bind to 8888
+
+IP-address of this machine will be used to initialize ```TVM_IOS_RPC_PROXY_HOST```
+environment variable (see below).
 
 ## Building
 Before start, please run ```init_proj.py``` to update XCode developer metadata. After this step, open
 ```tvmrpc.xcodeproj``` by using XCode, build the App and install the App on the phone. Usually, we
 **do not** use the iOS App directly.
 
+To test an App, you can fill ``Address`` field with IP-address of RPC proxy
+(see above), and press ``Connect to Proxy``.
+
+On success, "Disconnected" will change to "Connected".
+On RPC proxy side you can see the next message in a log:
+
+    INFO:root:Handler ready TCPSocketProxy:<iPhone IP address>:server:iphone
+
+Now App can be closed by pressing the home button (or even removed from a device).
+
 ## Workflow
 Due to security restriction of iOS10. We cannot upload dynamic libraries to the App and load it from sandbox.
 Instead, we need to build a list of libraries, pack them into the app bundle, launch the RPC server and
@@ -22,8 +44,12 @@ script, we don't need to manually operate the iOS App, this script will build th
 
 - ```TVM_IOS_CODESIGN``` The signature you use to codesign the app and libraries (e.g. ```iPhone Developer: Name (XXXX)```)
 - ```TVM_IOS_RPC_ROOT``` The root directory of the iOS rpc project
-- ```TVM_IOS_RPC_PROXY_HOST``` The RPC proxy address
-- ```TVM_IOS_RPC_DESTINATION``` The Xcode target device(e.g. ```platform=iOS,name=xxxx```)
+- ```TVM_IOS_RPC_PROXY_HOST``` The RPC proxy address (see above)
+- ```TVM_IOS_RPC_DESTINATION``` The Xcode target device (e.g. ```platform=iOS,id=xxxx```)
+
+See instructions of how to find UUID of the iOS device:
+
+- https://www.innerfence.com/howto/find-iphone-unique-device-identifier-udid
 
 ## How it works
 Let us explain how it works, the project look for ```rpc_config.txt``` file in the project root folder.
@@ -36,7 +62,7 @@ The ```rpc_config.txt``` file should be in the following format:
 ```
 The build script will copy all the dynamic libraries into bundle ```tvmrpc.app/Frameworks/tvm```,
 which you will be able to load via RPC using ```remote.load_module```.
-It will also create an ```tvmrpc.app/Frameworks/tvm/rpc_config.txt``` contaiing the first line.
+It will also create an ```tvmrpc.app/Frameworks/tvm/rpc_config.txt``` containing the first line.
 
 When we run the testcase, the testcase read the configuration from ```tvmrpc.app/Frameworks/tvm/rpc_config.txt```
 and connect to the specified RPC proxy, start serving loop.

apps/ios_rpc/tests/ios_rpc_test.py

@@ -6,6 +6,8 @@ And configure the proxy host field as commented.
 
 import tvm
 import os
+import re
+import sys
 from tvm import rpc
 from tvm.contrib import util, xcode
 import numpy as np
@@ -15,6 +17,12 @@ proxy_host = os.environ["TVM_IOS_RPC_PROXY_HOST"]
 # Set your desination via env variable.
 # Should in format "platform=iOS,id=<the test device uuid>"
 destination = os.environ["TVM_IOS_RPC_DESTINATION"]
+
+if not re.match(r"^platform=.*,id=.*$", destination):
+    print("Bad format: {}".format(destination))
+    print("Example of expected string: platform=iOS,id=1234567890abcabcabcabc1234567890abcabcab")
+    sys.exit(1)
+
 proxy_port = 9090
 key = "iphone"