server-on-computer.js

// Running on your computer.

var express = require('express');
var http = require('http');
var fs = require('fs');
var server = http.createServer();
var app = express();

server.on('request', app);

server.listen(3001, function () {
 console.log('Server on.');
});

app.post('/upload-pic', function (req, res, next) {

    console.log('Request received');

    var imageData = new Buffer(0);

    req.on('data', function (chunk) {
        imageData = Buffer.concat([imageData, chunk]);
    });

    req.on('end', function () {
       // Full image ready.
        fs.writeFile('./'+ Date.now().toString() + '.jpg', imageData);
    });

});

tessel-script.js

// Running on tessel.

var http = require('http');
var av = require('tessel-av');
var camera = new av.Camera();

var takePicture = camera.capture();

takePicture.on('data', function (image) {
    
    var request = http.request({
        hostname: '192.168.1.23', // Where your other process is running
        port: 3001,
        path: '/upload-pic',
        method: 'POST',
        headers: {
            'Content-Type': 'image/jpg',
            'Content-Length': image.length
        }
    });

    request.write(image);
    
});

takePicture.on('error', function (err) {
    console.error(err);
});