Streaming Data Using a Network Stream

Use network streams to stream data between two or more applications.

To transmit data using network streams, you must develop the code to write and read data on both the host and target applications.

What to Use

• Create Network Stream Writer Endpoint
• Create Network Stream Reader Endpoint
• Destroy Stream Endpoint
• Flush Stream
• Read Single Element from Stream
• Write Single Element to Stream
• While Loop

What to Do

1. Create the following diagram in a VI for the target application. This diagram illustrates the entire network stream code on the target application.

   Customize the gray sections for your unique programming goals.

   

   	The Create Network Stream Writer Endpoint node creates the writer endpoint in the target application.
   	The writer endpoint establishes a connection with the reader endpoint using the reader URL. Refer to the Details tab of the Create Network Stream Writer Endpoint or the Create Network Stream Reader Endpoint nodes for help specifying endpoint URLs.
   	The Write Single Element to Stream node continuously adds one data point to the FIFO buffer, which the reader endpoint on the host application reads from. Note You can use the Write Multiple Elements to the Stream node to add more than one data point at a time.
   	To specify the amount of time to wait between loop iterations, wire the desired time duration to the input of the Wait node. The Wait node waits until the value of the operating system's counter increases by an amount equal to the input you specify.
   	Data streams continuously until the user clicks the Stop button on the target application, which notifies the reader endpoint on the host application that the stream is no longer valid. Note You can also use the Stop button on the host application to stop streaming data.
   	The Flush Stream node transfers all data to the reader endpoint before data flow resumes. It ensures that all data still residing in the writer endpoint buffer immediately transfer across the network. The Flush Stream node then waits until either the specified wait condition is met or the timeout expires. Note Use this node before the Destroy Stream Endpoint node to ensure the reader endpoint receives all data before destroying the writer endpoint. This prevents data loss.
   	The Destroy Stream Endpoint node destroys the writer endpoint. To destroy a stream completely, however, you must destroy both the reader and writer endpoints.

2. Create the following diagram in a VI for the host application. This diagram illustrates the network stream code on the host application.

   Customize the gray sections for your unique programming goals.

   

   	The Create Network Stream Reader Endpoint node creates the reader endpoint on the host application. Once the reader endpoint exists, the writer endpoint will attempt to connect with it.
   	The Read Single Element from Stream node continuously consumes data from the FIFO buffer originally sent from the writer loop. Note The Read Multiple Elements from Stream node consumes batches of data from the buffer. You can use this node even if you used the Write Single Element to Stream node in the writer loop.
   	When the Destroy Stream Endpoint node destroys the writer endpoint, the reader endpoint receives an error, which causes the data flow to exit the While Loop. Note When the network disconnects, an endpoint becomes inactive. The other endpoint continuously tries to reestablish communication with the inactive endpoint in the background. This background process continues until the connection is repaired or until the inactive endpoint is destroyed.
   	The Destroy Stream Endpoint node destroys the reader endpoint, which destroys the stream.

After you finish developing your target and host applications, your target and host applications communicate using a network stream when you run the applications simultaneously. Be sure to run the target application first to ensure the writer endpoint can locate the reader endpoint.

Troubleshooting

• If you have trouble establishing a connection, try the following troubleshooting strategies:
  • Make sure you are using the recommended firewall settings.
  • (Windows 7) Make sure your Ethernet adapters are set to a "Home" or "Work" setting. If your network is set to Private, you may receive an error.
  • Make sure your endpoint URL is specified properly. Refer to the Details tab of the Create Network Stream Writer Endpoint or the Create Network Stream Reader Endpoint nodes for help specifying endpoint URLs.
  • Make sure you are not reusing endpoint names. If a name collision occurs, your intended endpoints will not connect and will error out. To avoid name collisions, consider using globally unique identifiers (GUID).
  • Make sure the endpoints you want to use are not connected to other endpoints. An endpoint can only connect to one other endpoint at a time.
  • Make sure you are specifying an endpoint that exists.
  • Make sure you are using compatible endpoints.
    • You cannot connect two reader endpoints to each other nor two writer endpoints to each other. You must use a writer endpoint and a reader endpoint.
    • The endpoints must have the same data type.
• If you have trouble streaming data after establishing a connection, try the following troubleshooting strategies:
  • Make sure the nodes are compatible with one another. You cannot wire a Read Multiple Elements from Stream node or a Read Single Element from Stream node to a Create Network Stream Writer Endpoint node. You also cannot wire a Write Multiple Elements to Stream node, a Write Single Element to Stream node, or a Flush Stream node to a Create Network Stream Reader Endpoint node.
  • Make sure you are not reading or writing a number of elements larger than the endpoint buffer size.

Examples