The **webSocket** module implements WebSocket connection management and operation.
> **NOTE**<br>
> The initial APIs of this module are supported since API version 6. Newly added APIs will be marked with a superscript to indicate their earliest API version.
> **NOTE**
>
> The initial APIs of this module are supported since API version 6. Newly added APIs will be marked with a superscript to indicate their earliest API version.
You can use WebSocket to establish a bidirectional connection between a server and a client. Before doing this, you need to use the [createWebSocket](#websocketcreatewebsocket) API to create a [WebSocket](#websocket) object and then use the [connect](#connect) API to connect to the server. If the connection is successful, the client will receive a callback of the [open](#onopen) event. Then, the client can communicate with the server using the [send](#send) API. When the server sends a message to the client, the client will receive a callback of the [message](#onmessage) event. If the client no longer needs this connection, it can call the [close](#close) API to disconnect from the server. Then, the client will receive a callback of the [close](#onclose) event.
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@@ -17,7 +16,7 @@ If an error occurs in any of the preceding processes, the client will receive a
importwebSocketfrom'@ohos.net.webSocket';
```
## Complete Example
## Examples
```js
importwebSocketfrom'@ohos.net.webSocket';
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@@ -37,7 +36,7 @@ ws.on('open', (err, value) => {
});
ws.on('message',(err,value)=>{
console.log("on message, message:"+value);
// When receiving the bye message (the actual message name may differ) from the server, the client proactively disconnects from the server.
// When receiving the `bye` message (the actual message name may differ) from the server, the client proactively disconnects from the server.
Initiates a WebSocket request carrying specified options to establish a WebSocket connection to a given URL. This API uses an asynchronous callback to return the result.
Initiates a WebSocket request carrying specified options to establish a WebSocket connection to a given URL. This API uses a promise to return the result.
>You can pass the callback of the **on** function if you want to cancel listening for a certain type of event. If you do not pass the callback, you will cancel listening for all events.
Enables listening for the **message** events of a WebSocket connection. This API uses an asynchronous callback to return the result. The maximum length of each message is 4 KB. If the length exceeds 4 KB, the message is automatically fragmented.
Disables listening for the **message** events of a WebSocket connection. This API uses an asynchronous callback to return the result. The maximum length of each message is 4 KB. If the length exceeds 4 KB, the message is automatically fragmented.
>The data in **AsyncCallback** can be in the format of string\(API 6\) or ArrayBuffer\(API 8\).
>You can pass the callback of the **on** function if you want to cancel listening for a certain type of event. If you do not pass the callback, you will cancel listening for all events.
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@@ -507,7 +559,7 @@ Enables listening for the **close** events of a WebSocket connection. This API u
```js
letws=webSocket.createWebSocket();
ws.on('close',(err,value)=>{
console.log("on close, code is "+value['code']+", reason is "+value['reason']);
console.log("on close, code is "+value.code+", reason is "+value.reason);
>You can pass the callback of the **on** function if you want to cancel listening for a certain type of event. If you do not pass the callback, you will cancel listening for all events.
>You can pass the callback of the **on** function if you want to cancel listening for a certain type of event. If you do not pass the callback, you will cancel listening for all events.
This error code is reported if an operation is not allowed.
**Cause**
The operation is illegal.
**Procedure**
Check the operation procedure.
## 2301002 File Not Exist
**Error Message**
No such file or directory.
**Description**
This error code is reported if the requested file does not exist.
**Cause**
The requested file does not exist.
**Procedure**
Check the file name or file path.
## 2301003 Process Not Exist
**Error Message**
No such process.
**Description**
This error code is reported if a process does not exist.
**Cause**
The process does not exist.
**Procedure**
Check the process information.
## 2301004 System Call Interrupted
**Error Message**
Interrupted system call.
**Description**
This error code is reported if the system call is interrupted.
**Cause**
The system call is interrupted.
**Procedure**
Rectify system call errors.
**Description of TCP/UDP error codes:**
> Mapping format of other TCP/UDP Socket error codes: 2301000 + Linux kernel error code (errno). For details, see Linux kernel error codes.
## 2300002 System Internal Error
**Error Message**
System internal error.
**Description**
This error code is reported if a system internal error occurs.
**Cause**
1. The memory is abnormal.
2. A null pointer is present.
**Procedure**
1. Check whether the memory space is sufficient. If not, clear the memory and try again.
2. Check whether the system is normal. If not, try again later or restart the device.
## 2303104 System Call Interrupted
**Error Message**
Interrupted system call.
**Description**
This error code is reported if the system call is interrupted.
**Cause**
Calling the **connect** function may result in a long blocking time. In such a case, the system generates an interrupt signal and returns an **EINTR** error.
**Procedure**
Call the **connect** function to try network connection again.
## 2303109 Error File Number
**Error Message**
Bad file number.
**Description**
This error code is reported if an operation is performed on a locally closed socket.
This error code is reported if the requested system resource is temporarily unavailable.
**Cause**
The system resources are in use.
**Procedure**
Try again later.
## 2303188 Socket Operations on Non-Sockets
**Error Message**
Socket operation on non-socket.
**Description**
This error code is reported if a socket descriptor is not specified for the **socket** parameter.
**Cause**
A socket descriptor is not specified for the **socket** parameter.
**Procedure**
Check whether the descriptor is correctly obtained.
## 2303191 Incorrect Socket Protocol Type
**Error Message**
Protocol wrong type for socket.
**Description**
This error code is reported if the type of the specified socket protocol is incorrect.
**Cause**
The **socket** function is called with an unsupported socket protocol type.
For example, the protocol type cannot be set to **SOCK_STREAM socket** for the the Internet UDP protocol.
**Procedure**
Check whether the socket protocol type is correct.
## 2303198 Network Address Already In Use
**Error Message**
Address already in use.
**Description**
This error code is reported if a network address has been used.
**Cause**
The probable cause can be any of the following: The application attempts to bind a socket to an IP address/port that has been used for an existing socket. The socket is not properly closed. The socket is still being closed.
**Procedure**
Try another network address.
## 2303199 Failed to Assign the Requested Address
**Error Message**
Cannot assign requested address.
**Description**
This error code is reported if the requested address is invalid in its context.
**Cause**
The remote address or port is invalid for the remote server.
**Procedure**
Check whether the address or port is correct.
## 2303210 Connection Timeout
**Error Message**
Connection timed out.
**Description**
This error code is reported if the connection to the remote server cannot be set up for a long time.
**Cause**
It is probable that a server breakdown has occurred.
**Procedure**
Contact the peer end to rectify the fault.
## 2303501 Null SSL
**Error Message**
SSL is null.
**Description**
This error code is reported if the SSL is null.
**Cause**
The returned error information is null when an internal function fails to be executed.
**Procedure**
Call the function again.
## 2303502 TLS Reading Error
**Error Message**
Error in tls reading.
**Description**
This error code is reported if an error occurs while reading data on the TLS socket.
**Cause**
The underlying socket is blocked.
**Procedure**
Perform data receiving again.
## 2303503 TLS Writing Error
**Error Message**
Error in tls writing.
**Description**
This error code is reported if an error occurs while writing data on the TLS socket.
**Cause**
When the send buffer is full, the underlying socket sends an **EWOUDLBLOCK** error, which means that the server does not read the data sent from the client.
**Procedure**
Rectify the fault on the server side.
## 2303504 x509 Failed to Look Up the x509 Certificate
**Error Message**
Error looking up x509.
**Description**
An error occurred when verifying the x509 certificate.
**Cause**
The local certificate does not match the server certificate.
**Procedure**
Check whether the local CA matches the server certificate.
## 2303505 TLS System Call Error
**Error Message**
Error occurred in the tls system call.
**Description**
This error code is reported if the TLS system call fails because of fatal I/O errors.
**Cause**
Network communication fails because of network faults.
**Procedure**
For details, see the Linux kernel error codes (errno).
## 2303506 Failed to Close TLS Connections
**Error Message**
Error clearing tls connection.
**Description**
This error code is reported if the TLS/SSL connection to be closed has been disabled.
**Cause**
The TLS/SSL connection to be closed has been disabled.
