I want to setup a consumer with amqp to read from a specific queue. Some googling pointed out that this can be done with amqp_basic_get, and looking into the documentation, the actual message is retrieved with amqp_read_message. I also found this example which I tried to follow for implementing the basic_get. Nevertheless, I am failing to get and read a message from a specific queue.
My scenario is like this: I have two programs that communicate by publishing and consuming from the rabbitmq server. In each, a connection is declared, with two channels, one meant for consuming, and one for publishing. The flow of information is like this: program A gets the current time and publishes to rabbitmq. Upon receiving this message, program B gets its own time, packages its time and the received time in a message that it publishes to rabbitmq. Program A should consume this message. However, I cannot succeed in reading from the namedQueue.
Program A (in c++, and uses the amqp.c) is implemented as follows:
... after creating the connection
//Create channels
amqp_channel_open_ok_t *res = amqp_channel_open(conn, channelIDPub);
assert(res != NULL);
amqp_channel_open_ok_t *res2 = amqp_channel_open(conn, channelIDSub);
assert(res2 != NULL);
//Declare exchange
exchange = "exchangeName";
exchangetype = "direct";
amqp_exchange_declare(conn, channelIDPub, amqp_cstring_bytes(exchange.c_str()),
amqp_cstring_bytes(exchangetype.c_str()), 0, 0, 0, 0,
amqp_empty_table);
...
throw_on_amqp_error(amqp_get_rpc_reply(conn), printText.c_str());
//Bind the exchange to the queue
const char* qname = "namedQueue";
amqp_bytes_t queue = amqp_bytes_malloc_dup(amqp_cstring_bytes(qname));
amqp_queue_declare_ok_t *r = amqp_queue_declare(
conn, channelIDSub, queue, 0, 0, 0, 0, amqp_empty_table);
throw_on_amqp_error(amqp_get_rpc_reply(conn), "Declaring queue");
if (queue.bytes == NULL) {
fprintf(stderr, "Out of memory while copying queue name");
return;
}
amqp_queue_bind(conn, channelIDSub, queue, amqp_cstring_bytes(exchange.c_str()),
amqp_cstring_bytes(queueBindingKey.c_str()), amqp_empty_table);
throw_on_amqp_error(amqp_get_rpc_reply(conn), "Binding queue");
amqp_basic_consume(conn, channelIDSub, queue, amqp_empty_bytes, 0, 0, 1,
amqp_empty_table);
throw_on_amqp_error(amqp_get_rpc_reply(conn), "Consuming");
// ...
// In order to get a message from rabbitmq
amqp_rpc_reply_t res, res2;
amqp_message_t message;
amqp_boolean_t no_ack = false;
amqp_maybe_release_buffers(conn);
printf("were here, with queue name %s, on channel %d\n", queueName, channelIDSub);
amqp_time_t deadline;
struct timeval timeout = { 1 , 0 };//same timeout used in consume(json)
int time_rc = amqp_time_from_now(&deadline, &timeout);
assert(time_rc == AMQP_STATUS_OK);
do {
res = amqp_basic_get(conn, channelIDSub, amqp_cstring_bytes("namedQueue"), no_ack);
} while (res.reply_type == AMQP_RESPONSE_NORMAL &&
res.reply.id == AMQP_BASIC_GET_EMPTY_METHOD
&& amqp_time_has_past(deadline) == AMQP_STATUS_OK);
if (AMQP_RESPONSE_NORMAL != res.reply_type || AMQP_BASIC_GET_OK_METHOD != res.reply.id)
{
printf("amqp_basic_get error codes amqp_response_normal %d, amqp_basic_get_ok_method %d\n", res.reply_type, res.reply.id);
return false;
}
res2 = amqp_read_message(conn,channelID,&message,0);
printf("error %s\n", amqp_error_string2(res2.library_error));
printf("5:reply type %d\n", res2.reply_type);
if (AMQP_RESPONSE_NORMAL != res2.reply_type) {
printf("6:reply type %d\n", res2.reply_type);
return false;
}
payload = std::string(reinterpret_cast< char const * >(message.body.bytes), message.body.len);
printf("then were here\n %s", payload.c_str());
amqp_destroy_message(&message);
Program B (in python) is as follows
#!/usr/bin/env python3
import pika
import json
from datetime import datetime, timezone
import time
import threading
cosimTime = 0.0
newData = False
lock = threading.Lock()
thread_stop = False
connection = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
connectionPublish = pika.BlockingConnection(pika.ConnectionParameters('localhost'))
channelConsume = connection.channel()
channelPublish = connectionPublish.channel()
print("Declaring exchange")
channelConsume.exchange_declare(exchange='exchangeName', exchange_type='direct')
channelPublish.exchange_declare(exchange='exchangeName', exchange_type='direct')
print("Creating queue")
result = channelConsume.queue_declare(queue='', exclusive=True)
queue_name = result.method.queue
result2 = channelPublish.queue_declare(queue='namedQueue', exclusive=False, auto_delete=False)
channelConsume.queue_bind(exchange='exchangeName', queue=queue_name,
routing_key='fromB')
channelPublish.queue_bind(exchange='exchangeName', queue="namedQueue",
routing_key='toB')
print(' [*] Waiting for logs. To exit press CTRL+C')
def callbackConsume(ch, method, properties, body):
global newData, cosimTime
print("\nReceived [x] %r" % body)
#cosimTime = datetime.datetime.strptime(body, "%Y-%m-%dT%H:%M:%S.%f%z")
with lock:
newData = True
cosimTime = body.decode()
cosimTime = json.loads(cosimTime)
#print(cosimTime)
def publishRtime():
global newData
while not thread_stop:
if newData:
#if True:
with lock:
newData = False
msg = {}
msg['rtime'] = datetime.now(timezone.utc).astimezone().isoformat(timespec='milliseconds')
msg['cosimtime'] = cosimTime["simAtTime"]
print("\nSending [y] %s" % str(msg))
channelPublish.basic_publish(exchange='exchangeName',
routing_key='toB',
body=json.dumps(msg))
#time.sleep(1)
channelConsume.basic_consume(
queue=queue_name, on_message_callback=callbackConsume, auto_ack=True)
try:
thread = threading.Thread(target = publishRtime)
thread.start()
channelConsume.start_consuming()
except KeyboardInterrupt:
print("Exiting...")
channelConsume.stop_consuming()
thread_stop = True
connection.close()
What program A outputs is:
amqp_basic_get error codes amqp_response_normal 1, amqp_basic_get_ok_method 3932232
which is the code for AMQP_BASIC_GET_EMPTY_METHOD.
Program B gets the data, and publishes continuously.
If I slightly modify B to just publish all the time a specific string, then it seems that the amqp_basic_get returns successfully, however then it fails at amqp_read_message with the code AMQP_RESPONSE_LIBRARY_EXCEPTION.
Any idea how to get this to work, what I am missing the setup?
The issue was in the queue_declare where the auto_delete parameter was not matching on both sides.
I am discovering the Plc4x java implementation which seems to be of great interest in our field. But the youth of the project and the documentation makes us hesitate. I have been able to implement the basic hello world for reading out of our PLCs, but I was unable to write. I could not find how the addresses are handled and what the maskwrite, andMask and orMask fields mean.
Please can somebody explain to me the following example and detail how the addresses should be used?
#Test
void testWriteToPlc() {
// Establish a connection to the plc using the url provided as first argument
try( PlcConnection plcConnection = new PlcDriverManager().getConnection( "modbus:tcp://1.1.2.1" ) ){
// Create a new read request:
// - Give the single item requested the alias name "value"
var builder = plcConnection.writeRequestBuilder();
builder.addItem( "value-" + 1, "maskwrite:1[1]/2/3", 2 );
var writeRequest = builder.build();
LOGGER.info( "Synchronous request ..." );
var syncResponse = writeRequest.execute().get();
}catch(Exception e){
e.printStackTrace();
}
}
I have used PLC4x for writing using the modbus driver with success. Here is some sample code I am using:
public static void writePlc4x(ProtocolConnection connection, String registerName, byte[] writeRegister, int offset)
throws InterruptedException {
// modbus write works ok writing one record per request/item
int size = 1;
PlcWriteRequest.Builder writeBuilder = connection.writeRequestBuilder();
if (writeRegister.length == 2) {
writeBuilder.addItem(registerName, "register:" + offset + "[" + size + "]", writeRegister);
}
...
PlcWriteRequest request = writeBuilder.build();
request.execute().whenComplete((writeResponse, error) -> {
assertNotNull(writeResponse);
});
Thread.sleep((long) (sleepWait4Write * writeRegister.length * 1000));
}
In the case of modbus writing there is an issue regarding the return of the writer Future, but the write is done. In the modbus use case I don't need any mask stuff.
Could you please help me to solve problem with thic THINC-API?
I inspected my CNC with SCOUT and got following information:
ApiSpec=False
ThincApiInstalled=True
ApiInstallType=Basic
ThincApiCheckResult=VersionRecognized
ThincApiVersion=1.12.1.0-SPEC_NOT_ACTIVE
What should i do to get access to data?
Your machine does not have the proper specification.
Custom API (CAPI)
Lathe and Multi-Tasking Machines: NC-B Spec No. 4, Bit 0
Machining Center: NC Spec No. 32, Bit 2
You can confirm in your program if a machine has this spec code enabled by using SCOUT:
bool HasCustomAPI = false;
if (Okuma.Scout.Platform.BaseMachineType == Okuma.Scout.Enums.MachineType.L)
{
if (Okuma.Scout.SpecCode.NCB.MachineSpecCodeFileExists)
{
if (Okuma.Scout.SpecCode.NCB.SpecFileIsValid)
{
HasCustomAPI = Okuma.Scout.SpecCode.NCB.Bit(
Okuma.Scout.Enums.NCBSpecGroup.NCB1MG, 4, 0);
}
}
}
else if (Okuma.Scout.Platform.BaseMachineType == Okuma.Scout.Enums.MachineType.M)
{
if (Okuma.Scout.SpecCode.NC.MachineSpecCodeFileExists)
{
if (Okuma.Scout.SpecCode.NC.SpecFileIsValid)
{
HasCustomAPI = Okuma.Scout.SpecCode.NC.Bit(
Okuma.Scout.Enums.NCSpecGroup.NC1MG, 32, 2);
}
}
}
if (HasCustomAPI)
{
// ...
}
The Okuma Open API (THINC API) requires this spec code to function.
It comes standard with machines sold in the USA.
For other counties, this is an option you will need to order.
Please contact your Okuma Representative.
I have found some suggestions on how to add a block to a page, but can't get it to work the way I want, so perhaps someone can help out.
What I want to do is to have a scheduled job that reads through a file, creating new pages with a certain pagetype and in the new page adding some blocks to a content property. The blocks fields will be updated with data from the file that is read.
I have the following code in the scheduled job, but it fails at
repo.Save((IContent) newBlock, SaveAction.Publish);
giving the error
The page name must contain at least one visible character.
This is my code:
public override string Execute()
{
//Call OnStatusChanged to periodically notify progress of job for manually started jobs
OnStatusChanged(String.Format("Starting execution of {0}", this.GetType()));
//Create Person page
PageReference parent = PageReference.StartPage;
//IContentRepository contentRepository = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance<IContentRepository>();
//IContentTypeRepository contentTypeRepository = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance<IContentTypeRepository>();
//var repository = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance<IContentRepository>();
//var slaegtPage = repository.GetDefault<SlaegtPage>(ContentReference.StartPage);
IContentRepository contentRepository = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance<IContentRepository>();
IContentTypeRepository contentTypeRepository = EPiServer.ServiceLocation.ServiceLocator.Current.GetInstance<IContentTypeRepository>();
SlaegtPage slaegtPage = contentRepository.GetDefault<SlaegtPage>(parent, contentTypeRepository.Load("SlaegtPage").ID);
if (slaegtPage.MainContentArea == null) {
slaegtPage.MainContentArea = new ContentArea();
}
slaegtPage.PageName = "001 Kim";
//Create block
var repo = ServiceLocator.Current.GetInstance<IContentRepository>();
var newBlock = repo.GetDefault<SlaegtPersonBlock1>(ContentReference.GlobalBlockFolder);
newBlock.PersonId = "001";
newBlock.PersonName = "Kim";
newBlock.PersonBirthdate = "01 jan 1901";
repo.Save((IContent) newBlock, SaveAction.Publish);
//Add block
slaegtPage.MainContentArea.Items.Add(new ContentAreaItem
{
ContentLink = ((IContent) newBlock).ContentLink
});
slaegtPage.URLSegment = UrlSegment.CreateUrlSegment(slaegtPage);
contentRepository.Save(slaegtPage, EPiServer.DataAccess.SaveAction.Publish);
_stopSignaled = true;
//For long running jobs periodically check if stop is signaled and if so stop execution
if (_stopSignaled) {
return "Stop of job was called";
}
return "Change to message that describes outcome of execution";
}
You can set the Name by
((IContent) newBlock).Name = "MyName";
What's the best way to receive 'hidden' input from a command-line Dart application? For example, in Bash, this is accomplished with:
read -s SOME_VAR
Set io.stdin.echoMode to false:
import 'dart:io' as io;
void main() {
io.stdin.echoMode = false;
String input = io.stdin.readLineSync();
// or
var input;
while(input != 32) {
input = io.stdin.readByteSync();
if(input != 10) print(input);
}
// restore echoMode
io.stdin.echoMode = true;
}
This is a slightly extended version, key differences are that it uses a finally block to ensure the mode is reset if an exception is thrown whilst the code is executing.
The code also uses a waitFor call (only available in dart cli apps) to turn this code into a synchronous call. Given this is a cli command there is no need for the complications that futures bring to the table.
The code also does the classic output of '*' as you type.
If you are doing much cli work the below code is from the dart package I'm working on called dcli. Have a look at the 'ask' method.
https://pub.dev/packages/dcli
String readHidden() {
var line = <int>[];
try {
stdin.echoMode = false;
stdin.lineMode = false;
int char;
do {
char = stdin.readByteSync();
if (char != 10) {
stdout.write('*');
// we must wait for flush as only one flush can be outstanding at a time.
waitFor<void>(stdout.flush());
line.add(char);
}
} while (char != 10);
} finally {
stdin.echoMode = true;
stdin.lineMode = true;
}
// output a newline as we have suppressed it.
print('');
return Encoding.getByName('utf-8').decode(line);
}