![\"\"](\"https:\/\/visualgdb.com\/w\/wp-content\/uploads\/2022\/08\/05a-share.png\")
<\/a><\/li>\n<\/a><\/li>\n<\/a><\/li>\n<\/a><\/li>\n<\/a><\/li>\n<\/a>If you are using a custom board with a different name and VisualGDB does not show the SSID\/Password prompt, try editing the\u00a0BoardWithWiFi<\/strong> element in the <VisualGDB Directory>\\Rules\\PicoSDK.xml<\/strong> file. The element contains a regular expression that can cover multiple board names.<\/li>\n<\/a><\/li>\n<\/a>You can use the Test button to instantly verify that OpenOCD can connect to the target via SWD.<\/li>\n<\/a>This will redirect the output from printf()<\/strong> to the VisualGDB Output<\/strong> window, so you won’t need to setup the UART connection. If you do not need the printf()<\/strong> output, you can skip this step.<\/li>\n<\/a><\/li>\n- \n
- First it connects to the Wi-Fi network by calling\u00a0cyw43_arch_enable_sta_mode()<\/strong> and cyw43_arch_wifi_connect_timeout_ms().<\/strong><\/li>\n
- Then it calls the tcp_server_open()<\/strong> function that:\n
- \n
- Creates a new TCP connection object by calling tcp_new_ip_type().<\/strong><\/li>\n
- Binds it to port 4242 by calling tcp_bind() <\/strong>and then starts listening for incoming connections by calling tcp_listen_with_backlog().<\/strong><\/li>\n
- Configures lwIP to call the tcp_server_accept()<\/strong> callback whenever anyone connects to the TCP port.<\/li>\n<\/ul>\n<\/li>\n
- When a client connects to the TCP port 4242, the tcp_server_accept()<\/strong> callback sets 4 additional callbacks on the newly created connection:\n
- \n
- tcp_server_sent()<\/strong> that will be called by lwIP once it completed sending a chunk of data to the client.<\/li>\n
- tcp_server_recv()<\/strong> once it received data from the client.<\/li>\n
- tcp_server_poll()<\/strong> once there has not been any activity on the socket for 10 seconds (POLL_TIME_S<\/strong> * 2)<\/li>\n
- tcp_server_err()<\/strong> once the socket encounters an internal error.<\/li>\n<\/ol>\n<\/li>\n
- Once the callbacks are set, tcp_server_accept()<\/strong> sends a random payload to the client, expecting it to echo it back.<\/li>\n
- The tcp_server_recv()<\/strong> callback buffers the incoming data in the TCP_SERVER_T::buffer_recv<\/strong> buffer, and once the amount of received data matches the amount of sent data, it compares it against the sent block.<\/li>\n<\/ol>\n<\/li>\n
- Normally, the TCP server example would require a small test program that could receive and echo back a large random chunk of data, however we will modify it so that it could be tested with the telnet<\/strong> tool. First of all, locate the definition of BUF_SIZE and reduce it to 8. Then, locate the tcp_server_send_data()<\/strong> function and replace the initialization logic for buffer_sent with this:\n
memcpy(state->buffer_sent, \"test123\\r\", BUF_SIZE);<\/pre>\n<\/li>\n
- Now set a breakpoint at the tcp_write()<\/strong> call and press F5 to build the project and begin debugging it:
![\"\"](\"https:\/\/visualgdb.com\/w\/wp-content\/uploads\/2022\/08\/09-bkpt.png\")
<\/a><\/li>\n- Wait for the board to connect to the Wi-Fi network (it will report the IP address it got via the printf()<\/strong> output) and run “telnet <Board IP> 4242” on your Windows machine. Telnet will connect to the board and the breakpoint in tcp_server_send_data()<\/strong> will trigger:
![\"\"](\"https:\/\/visualgdb.com\/w\/wp-content\/uploads\/2022\/08\/10-connected.png\")
<\/a><\/li>\n- Note that due to security considerations, Windows does not have the telnet client installed by default. You can install it via Control Panel -> Add\/Remove Programs->Turn Windows features on and off -> Telnet Client<\/strong>:
![\"\"](\"https:\/\/visualgdb.com\/w\/wp-content\/uploads\/2022\/08\/telnet.png\")
<\/a><\/li>\n- Press F5 to continue debugging. Go to the telnet client, type “test123<\/strong>” and press <ENTER>. The board will show a series of “tcp_server_recv X\/Y err 0”<\/strong> messages in the semihosting console (one for each received packet) and will finally call tcp_server_send_data()<\/strong> to do another round of tests:
![\"\"](\"https:\/\/visualgdb.com\/w\/wp-content\/uploads\/2022\/08\/11-pass2.png\")
<\/a><\/li>\n<\/ol>\nNote that the TCP server example shown in this tutorial does not use FreeRTOS, so it has to do handle ALL<\/strong> the connections inside the one and only thread, forcing the use of the callbacks instead of the classic socket API. For all practical purposes, we recommend using FreeRTOS-based projects instead.<\/p>\n
- tcp_server_recv()<\/strong> once it received data from the client.<\/li>\n
- Binds it to port 4242 by calling tcp_bind() <\/strong>and then starts listening for incoming connections by calling tcp_listen_with_backlog().<\/strong><\/li>\n
- Then it calls the tcp_server_open()<\/strong> function that:\n