error handling, long holding time after catching an error?

[g-zajac]

I use the function below to connect, read registers and disconnect from a modbus device:

async function readRegisters(ip, registerAddress, numberOfRegisters){
  try {
    client.setID(1);
    client.setTimeout(1000);
    await client.connectTCP(ip, {port: 502})
    const regs =  await client.readHoldingRegisters(registerAddress, numberOfRegisters);
    return regs;
  }
  catch (e) {
    return e
  }
  finally {
    client.close();
  }
}

and run it:

readRegisters("192.168.1.10", 1, 5)
.then((readings) => {console.log("readings:", readings);})
.catch((error) => {console.log("error: ", error);})

When I run it with a modbus device connected it works fine. When the device is disconnected it outputs an error but then hangs for long time, like a minute or so till function finishes. How can I reduce this time?

[yaacov]

Hi, thank you for the issue.

their was a change 2 days ago in the code that handle that: https://github.com/yaacov/node-modbus-serial/pull/347

can you use the code from github (not npm) and see if current development code fixes your issue ?

[g-zajac]

Hi, thank you for prompt answer. I have uninstalled the npm modbus-serial package and installed it again from git: "modbus-serial": "git+https://github.com/yaacov/node-modbus-serial.git" still the same I'm afraid. I use modbus for controlling Moons SSDC10-D and stepper motors. It connects, reads registers and closes connection quickly with no issues. But if there is no device I got caught error message immediately and around 1min till disconnecting. Any suggestions?

[yaacov]

a - can you try to set the timeout in the potions ? e.g. await client.connectTCP(ip, {port: 502, timeout: 1000}) b - can you try and remove the override in: https://github.com/yaacov/node-modbus-serial/blob/master/apis/connection.js#L107 and see if it changes something ? (after you added the timeout in the options :-))

[g-zajac]

I have added timeout to options:

async function readRegisters(ip, registerAddress, numberOfRegisters){
  try {
    client.setID(1);
    client.setTimeout(999);
    await client.connectTCP(ip, {port: 502, timeout: 888})
    const regs =  await client.readHoldingRegisters(registerAddress, numberOfRegisters);
    return regs.data;
  }
  catch (e) {
    return "modbus connection error"
  }
  finally {
    client.close();
  }
}

I have log out from the apis/connection.js section if (this._timeout) {... this._timeout = 999 options.timeout before overriding : 888 options.timeout after overriding : 999

Commenting out the if(this._timeout) section and adding timeout in options does not change the disconnection time, still long.

[yaacov]

hmmm... so the next place to search is: https://github.com/yaacov/node-modbus-serial/blob/master/ports/tcpport.js#L137

can you set a timout after the open call ?

timer = setTimeout(function() {
            // check what is going on :-)
}, timeout);

we can printout the state of the socket, maybe force close it if not connection is done and we hit the timer / emit timeout signal / soemthing else ... ?

[g-zajac]

Hi, I have added a setTimeout like this:

async function readCoils(ip, coilAddress, numberOfCoils){
  try {
    setTimeout( () => {
      local_client.close;
    }, 900);

    var local_client = new ModbusRTU();
    local_client.setID(clientID);
    local_client.setTimeout(1000);
    await local_client.connectTCP(ip, {port: 502})
    const coils =  await local_client.readCoils(coilAddress, numberOfCoils);
    return coils.data;
  }
  catch (e) {
    return {connected: false}
  }
  finally {
    local_client.close();
  }
}

still the same, throws error: TCP Connection Timed Out {"stack":"Error: TCP Connection Timed Out\n at Socket.<anonymous> (/server/node_modules/modbus-serial/ports/tcpport.js:11 1:24)\n at Socket.emit (events.js:198:13)\n at Socket._onTimeout (net.js:442:8)\n at ontimeout (timers.js:436:11)\n at tryOnTimeout (timers.js:300:5)\n at listOnTimeout (timers.js:263:5)\n at Timer.processTimers (timers.js:223:10)"} and hang about for a minute when modbus device disconnected, even when timeOut calls. Any suggestions how can I force connection close please?