Test TCP Functionality With OT CLI

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OpenThread offers TCP commands for use with a Thread network to test peer-to-peer communication between TCP endpoints. The cli tcp provides one sample TCP endpoint and one sample TCP listener with which all tcpcommands interact.

Command overviews and the example that follows provide information on initializing the example TCP endpoint and TCP listener, how to connect to a peer TCP endpoint, and how to send a message to the peer.

TCP commands

For a list of tcp commands, type help: 

tcp help
abort
benchmark
bind
connect
deinit
init
listen
send
sendend
stoplistening
Done
For descriptions and syntax of all commands, refer to the CLI Command Reference. The TCP commands begin alphabetically with tcp abort.

init command

Use the tcp init command to initialize the TCP module to begin TCP communication. The TCP module can then perform many functions, such as listening for incoming connections using the example TCP listener provided by the tcp CLI. To deinitialize the example TCP listener and the example TCP endpoint, issue the tcp deinit command.

bind command

To bind the example TCP endpoint once you have initialized the TCP module, run a tcp bind command to assign an IPv6 address and a port to the TCP endpoint. This binds the endpoint for communication. Assigning the IPv6 address and port is also referred to as "naming the endpoint."

listen command

To use the example TCP listener once you have initialized the TCP module, run a tcp listen command and specify the IPv6 address and listening port.

To stop the example TCP listener from listening for incoming TCP connections, issue the tcp stoplistening command.

connect command

A tcp connect command connects the example TCP endpoint to a peer TCP endpoint address.

send command

Once a connection is established between two nodes, issue a tcp send command to send a message to the peer.

benchmark commands

Once a TCP connection is established between two nodes, optionally use the benchmark commands to send large amounts of data between the nodes to test network bandwidth and performance. The number of transmitted bytes in milliseconds as well as the TCP Goodput will be provided in the benchmark results.

abort command

To immediately and unceremoniously end a TCP connection, run the tcp abort command on either node to transition the TCP endpoint to a closed state.

sendend command

When one node is done sending data to the other node, the first node can issue a tcp sendend command to alert the second node to no longer expect data. The second node can also send a tcp sendend to the first node. Once each node receives a TCP: Disconnected message, the TCP connection between the two nodes is torn down. It is recommended but not required to issue this command when data transfer is complete.

Send a message between two nodes

  1. On node 1, initialize the TCP CLI module, then listen for incoming connections using the example TCP listener.

    tcp init
tcp listen :: 30000

    The use of :: denotes that the listen should use the unspecified IPv6 address, thereby having the TCP/IPv6 stack assign the IPv6 address. The port is 30000.

  2. On Node 2, initialize the TCP CLI module, connect to node 1, and then send a simple message. 

    tcp init
tcp connect fe80:0:0:0:a8df:580a:860:ffa4 30000
tcp send hello

Verification

Based on the example steps shown above, the following output would be expected:

  • After Node 2 runs the tcp connect command, Node 2 should receive the message TCP: Connection established.
  • Node 1 should then receive the messages (with example IPv6 address and port):
    • Accepted connection from [fe80:0:0:0:8f3:f602:bf9b:52f2]:49152
    • TCP: Connection established
  • After Node 2 runs the tcp send command, Node 1 should receive the message TCP: Received 5 bytes: hello