# call()

### call(topicURI\[, payload\[, advancedOptions]])

Make an RPC call to topicURI.

Parameters:

* **topicURI**. Required. A string that identifies the remote procedure to be called. Must meet a WAMP Spec URI requirements.
* **payload**. RPC data. Optional. Maybe any single value or array or hash-table object or null:
  * If it is an array - it is sent as is as WAMP positional arguments attribute
  * If it is a single object (without **argsList** and **argsDict** keys) - it is sent as is as WAMP key-value arguments attribute
  * If it is a single Number/String/Boolean/Null value - it is packed into a one-item array and is sent as WAMP positional arguments attribute. Be aware that the receiver will get it in argsList as a one-item array and not as a single value!
  * It is possible to pass the array and object-like data simultaneously. In this case, pass a hash-table with the next attributes:
    * **argsList**: array payload (may be omitted)
    * **argsDict**: object payload (may be omitted)
* **advancedOptions**. Optional parameters hash table. Must include any or all of the options:
  * **disclose\_me**: bool flag of disclosure of Caller identity (WAMP session ID) to endpoints of a routed call
  * **progress\_callback**: function for handling intermediate progressive call results
  * **timeout**: integer timeout (in ms) for the call to finish
  * **ppt\_scheme**: string Identifies the Payload Schema for Payload Passthru Mode
  * **ppt\_serializer**: string Specifies what serializer was used to encode the payload
  * **ppt\_cipher**: string Specifies the cryptographic algorithm that was used to encrypt the payload
  * **ppt\_keyid**: string Contains the encryption key id that was used to encrypt the payload

Returns `promise`:

* Resolved with one hash-table parameter with the following attributes:
  * **details**: hash-table with some additional details
  * **argsList**: an optional array containing the original list of positional result elements as returned by the *Callee*
  * **argsDict**: optional hash-table containing the original dictionary of keyword result elements as returned by the *Callee*
* Rejected with one of the [Errors instances](https://ksdaemon.gitbook.io/wampy.js/api/broken-reference)

**Important note on progressive call results**:

For getting progressive call results you need to specify `progress_callback` in `advancedOptions`. This callback will be fired on every intermediate result. **But** the last one result or error will be processed on promise returned from the `.call()`. That means that final call result will be received by call promise `resolve` handler.

```javascript
let result = await ws.call('server.time');
console.log('Server time is ' + result.argsList[0]);

try {
    await ws.call('start.migration');
    console.log('RPC successfully called');
} catch (e) {
    console.log('RPC call failed!', e.error);
}

try {
    await ws.call('restore.backup', { backupFile: 'backup.zip' });
    console.log('Backup successfully restored');
} catch (e) {
    console.log('Restore failed!', e.error, e.details);
}
```