Styjun

I'm connecting a remote client to a c application via a node.js service and am having trouble separating the printf() statements from the c application when output from the node.js app.

When the printf() statements happen in quick succession, the node.js application prints them together. This is causing errors for the client parsing that output.

As I'm new to c and still early in node.js, my testing has lead me to guess that the issue is related to how node.js handles the stdout stream from the child_process.

I should also note that the output is not consistently incorrect. There are a few places in the code where it's more variable and correlated to the speed of user inputs (this is for a game). The example I've shared below is the case where the output most consistently incorrect.

I've tried:

• Running the c program directly. (This gives me the expected [correct] result)


• Adjusting the buffer size in c with setvbuf (Unexpected result from the node.js application)


• Running the c application from node with the synchronous and asynchronous versions of both spawn and exec (Unexpected result from the node.js application)

Here's a portion of the c application:

void readPin(int outputPin)

 if(output[lightPins[light]] == outputPin)
 reportGameStatus("light match");
 lightSuccess();
 
 ...


void lightSuccess()
 reportGameStatus("light success");
 ...



void reportGameStatus(char* event)
 printf(""
 ""event":"%s","
 "n",
 event
 );

 fflush(stdout);

And here's the node.js portion:

var spawn = require("child_process").spawn;
var process = spawn("./cApplication");

process.stdout.on('data',function(msg)
 console.log('stdout: ' + msg);
 ...
);

This results in the following output from the node.js application:

stdout: "event":"light match""event":"light success"

Expected result:

stdout: "event":"light match"
stdout: "event":"light success"