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215 lines
5.3 KiB
Markdown
215 lines
5.3 KiB
Markdown
| [Home](/trick) → [Documentation Home](../Documentation-Home) → [Web Server](Webserver) → [APIs](WebServerAPIs) → WS Variable Server API |
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# WS-API: VariableServer
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```ws://localhost:8888/api/ws/VariableServer```
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## Purpose
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JSON Variable Server
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## Client to Server Command Messages
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Add a Trick Variable to the current session.
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```json
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{ "cmd" : "var_add",
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"var_name" : string
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}
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```
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Stop sending periodic ```var_list``` messages (*see below*) from the server.
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```json
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{ "cmd" : "var_pause" }
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```
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Resume sending periodic ```var_list``` response messages from the server.
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```json
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{ "cmd" : "var_unpause" }
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```
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Send one ```var_list``` message from the server.
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```json
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{ "cmd" : "var_send" }
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```
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Clear all variables from the current session, that is: undo all of the ```var_add``` commands.
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```json
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{ "cmd" : "var_clear" }
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```
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Disconnect from the variable server.
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```json
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{ "cmd" : "var_exit" }
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```
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Set the period (in milliseconds) at which ```var_list``` messages are sent form the server.
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```json
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{ "cmd" : "var_cycle",
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"period" : integer
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}
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```
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Execute the given Python code in the host sim.
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```json
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{ "cmd" : "python",
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"pycode" : string
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}
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```
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Send the sie structure from the server. Response will be the ```sie``` response message (*below*).
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```json
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{ "cmd" : "sie" }
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```
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Send the units for the given variable. Response will be the ```units``` response message (*below*).
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```json
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{ "cmd" : "units",
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"var_name" : string
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}
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```
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## Server to Client Response Messages
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Error Response
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```json
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{ "msg_type" : "error",
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"error_text" : string
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}
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```
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Periodic response containing the values of variables requested by ```var_add```.
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```json
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{ "msg_type" : "var_list"
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"time" : double
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"values" : []
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}
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```
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Response to the ```sie``` command (*above*).
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```json
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{ "msg_type" : "sie",
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"data" : string
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}
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```
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Response to the ```units``` command (*above*).
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```json
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{ "msg_type" : "units",
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"var_name" : string,
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"data" : string
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}
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```
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## Example Variable Server Client
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```html
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<!DOCTYPE html>
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<html>
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<head>
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<title>WS Experiments</title>
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</head>
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<body>
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<style>
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table { border-collapse: collapse; width: 100%; }
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th, td { text-align: left; padding: 8px; }
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tr:nth-child(even){background-color: #f2f2f2}
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th { background-color: #562399; color: white; }
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</style>
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<header>
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</header>
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<div class="variableDisplay"></div>
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<table class="variables">
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<tr>
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<th>Variable</th>
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<th>Value</th>
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</tr>
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</table>
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<div id="output"></div>
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<script type="text/javascript">
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function log(s) {
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var p = document.createElement("p");
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p.style.wordWrap = "break-word";
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p.textContent = s;
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output.appendChild(p);
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}
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function sendMessage(msg) {
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ws.send(msg);
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}
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// Interface to Trick WebSocket Variable Server
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function setPeriod(period) {
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sendMessage(`{"cmd":"var_cycle","period":${period}}`);
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}
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function addVarTableRow(name, value) {
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// create a row in the table that contains two <td>s, one for the var_name and one for its value.
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let tr = document.createElement('tr');
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let td1 = document.createElement('td');
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td1.textContent = `${name}`;
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let td2 = document.createElement('td');
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td2.textContent = `${value}`;
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td2.className = "values";
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tr.appendChild(td1);
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tr.appendChild(td2);
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varTable.appendChild(tr);
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}
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function addVariable(name, value) {
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sendMessage(`{"cmd":"var_add","var_name": "${name}"}`);
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addVarTableRow(name, value);
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}
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var varTable = document.querySelector('table.variables');
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var ws = new WebSocket('ws://localhost:8888/api/ws/VariableServer');
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ws.onopen = function(e) {
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setPeriod(100);
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addVarTableRow("Time", 0.0);
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addVariable("dyn.cannon.pos[0]", 0.0);
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addVariable("dyn.cannon.pos[1]", 0.0);
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addVariable("dyn.cannon.vel[0]", 0.0);
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addVariable("dyn.cannon.vel[1]", 0.0);
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addVariable("dyn.cannon.time", 0.0);
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addVariable("dyn.cannon.timeRate", 0.0);
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addVariable("dyn.cannon.impact", 0.0);
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addVariable("I.dont.exist", 0.0);
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sendMessage("{\"cmd\":\"var_unpause\"}");
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};
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ws.onmessage = function(e) {
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let msg = JSON.parse(e.data);
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if (msg.msg_type == "values") {
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let valueNodes = varTable.getElementsByClassName("values");
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valueNodes[0].textContent = msg.time;
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for (let i = 0; i < msg.values.length; i++ ) {
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valueNodes[i+1].textContent = msg.values[i];
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}
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}
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};
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ws.onerror = function(e) {
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console.log("WebSocket Error: " , e);
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handleErrors(e);
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};
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ws.onclose = function(e) {
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console.log("Connection closed", e);
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};
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</script>
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</body>
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</html>
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```
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Continue to [Extending the HTTP API](Extend-http-api) |