diff --git a/lib/workers/master.js b/lib/workers/master.js
index 300fbb9d..a6f7f60a 100644
--- a/lib/workers/master.js
+++ b/lib/workers/master.js
@@ -7,6 +7,7 @@
 
 'use strict';
 
+var assert = require('assert');
 var EventEmitter = require('events').EventEmitter;
 var util = require('../utils/util');
 var Network = require('../protocol/network');
@@ -31,6 +32,8 @@ function Master() {
 
   this.framer = new Framer();
   this.parser = new Parser();
+  this.env = {};
+  this.listening = false;
 
   this._init();
 }
@@ -45,41 +48,67 @@ util.inherits(Master, EventEmitter);
 Master.prototype._init = function _init() {
   var self = this;
 
-  if (util.isBrowser) {
-    global.onerror = function onerror(err) {
-      self.emit('error', err);
-    };
-    global.onmessage = function onmessage(event) {
-      var data;
-      if (typeof event.data !== 'string') {
-        data = event.data.buf;
-        data.__proto__ = Buffer.prototype;
-      } else {
-        data = new Buffer(event.data, 'hex');
-      }
-      self.emit('data', data);
-    };
-  } else {
-    process.stdin.on('data', function(data) {
-      self.emit('data', data);
-    });
-    // Nowhere to send these errors:
-    process.stdin.on('error', util.nop);
-    process.stdout.on('error', util.nop);
-    process.stderr.on('error', util.nop);
-  }
-
   this.on('data', function(data) {
     self.parser.feed(data);
   });
 
-  this.parser.on('error', function(e) {
-    self.emit('error', e);
+  this.parser.on('error', function(err) {
+    self.emit('error', err);
   });
 
   this.parser.on('packet', function(packet) {
     self.emit('packet', packet);
   });
+
+  if (util.isBrowser) {
+    // Web workers
+    this._initWebWorkers();
+  } else {
+    // Child process + pipes
+    this._initChildProcess();
+  }
+};
+
+/**
+ * Initialize master (web workers).
+ * @private
+ */
+
+Master.prototype._initWebWorkers = function _initWebWorkers() {
+  var self = this;
+
+  global.onerror = function onerror(err) {
+    self.emit('error', err);
+  };
+
+  global.onmessage = function onmessage(event) {
+    var data;
+    if (typeof event.data !== 'string') {
+      data = event.data.buf;
+      data.__proto__ = Buffer.prototype;
+    } else {
+      data = new Buffer(event.data, 'hex');
+    }
+    self.emit('data', data);
+  };
+};
+
+/**
+ * Initialize master (node.js).
+ * @private
+ */
+
+Master.prototype._initChildProcess = function _initChildProcess() {
+  var self = this;
+
+  process.stdin.on('data', function(data) {
+    self.emit('data', data);
+  });
+
+  // Nowhere to send these errors:
+  process.stdin.on('error', util.nop);
+  process.stdout.on('error', util.nop);
+  process.stderr.on('error', util.nop);
 };
 
 /**
@@ -172,6 +201,11 @@ Master.prototype.log = function log() {
 Master.prototype.listen = function listen(env) {
   var self = this;
 
+  assert(!this.listening, 'Already listening.');
+
+  this.env = env;
+  this.listening = true;
+
   Network.set(env.BCOIN_WORKER_NETWORK);
 
   util.log = this.log.bind(this);
@@ -182,23 +216,39 @@ Master.prototype.listen = function listen(env) {
   });
 
   this.on('packet', function(packet) {
-    var result;
-
-    switch (packet.cmd) {
-      case packets.types.EVENT:
-        self.emit('event', packet.items);
-        self.emit.apply(self, packet.items);
-        break;
-      case packets.types.ERROR:
-        self.emit('error', packet.error);
-        break;
-      default:
-        result = jobs.execute(packet);
-        result.id = packet.id;
-        self.send(result);
-        break;
+    try {
+      self.handlePacket(packet);
+    } catch (e) {
+      self.emit('error', e);
     }
   });
+
+  return this;
+};
+
+/**
+ * Handle packet.
+ * @private
+ * @param {Packet}
+ */
+
+Master.prototype.handlePacket = function handlePacket(packet) {
+  var result;
+
+  switch (packet.cmd) {
+    case packets.types.EVENT:
+      this.emit('event', packet.items);
+      this.emit.apply(this, packet.items);
+      break;
+    case packets.types.ERROR:
+      this.emit('error', packet.error);
+      break;
+    default:
+      result = jobs.execute(packet);
+      result.id = packet.id;
+      this.send(result);
+      break;
+  }
 };
 
 /*
diff --git a/lib/workers/packets.js b/lib/workers/packets.js
index 053bd769..b478a3a4 100644
--- a/lib/workers/packets.js
+++ b/lib/workers/packets.js
@@ -47,7 +47,6 @@ var packetTypes = {
 
 function Packet() {
   this.id = ++Packet.id >>> 0;
-  this.error = null;
 }
 
 Packet.id = 0;
diff --git a/lib/workers/workerpool.js b/lib/workers/workerpool.js
index 69470b06..00e3008c 100644
--- a/lib/workers/workerpool.js
+++ b/lib/workers/workerpool.js
@@ -410,6 +410,9 @@ function Worker(id) {
   this.id = id != null ? id : -1;
   this.child = null;
   this.pending = {};
+  this.env = {
+    BCOIN_WORKER_NETWORK: Network.type
+  };
 
   this._init();
 }
@@ -423,92 +426,105 @@ util.inherits(Worker, EventEmitter);
 
 Worker.prototype._init = function _init() {
   var self = this;
-  var penv;
-
-  penv = {
-    BCOIN_WORKER_NETWORK: Network.type
-  };
-
-  if (util.isBrowser) {
-    this.child = new global.Worker('/bcoin-worker.js');
-
-    this.child.onerror = function onerror(err) {
-      self.emit('error', err);
-      self.emit('exit', -1, null);
-    };
-
-    this.child.onmessage = function onmessage(event) {
-      var data;
-      if (typeof event.data !== 'string') {
-        data = event.data.buf;
-        data.__proto__ = Buffer.prototype;
-      } else {
-        data = new Buffer(event.data, 'hex');
-      }
-      self.emit('data', data);
-    };
-
-    this.child.postMessage(JSON.stringify(penv));
-  } else {
-    this.child = cp.spawn(process.argv[0], [__dirname + '/worker.js'], {
-      stdio: 'pipe',
-      env: util.merge({}, process.env, penv)
-    });
-
-    this.child.on('error', function(err) {
-      self.emit('error', err);
-    });
-
-    this.child.on('exit', function(code, signal) {
-      self.emit('exit', code == null ? -1 : code, signal);
-    });
-
-    this.child.on('close', function() {
-      self.emit('exit', -1, null);
-    });
-
-    this.child.stdin.on('error', function(err) {
-      self.emit('error', err);
-    });
-
-    this.child.stdout.on('error', function(err) {
-      self.emit('error', err);
-    });
-
-    this.child.stderr.on('error', function(err) {
-      self.emit('error', err);
-    });
-
-    this.child.stdout.on('data', function(data) {
-      self.emit('data', data);
-    });
-  }
-
-  this.on('exit', function() {
-    self.killJobs();
-  });
-
-  this.on('error', function() {
-    self.killJobs();
-  });
 
   this.on('data', function(data) {
     self.parser.feed(data);
   });
 
-  this.parser.on('error', function(e) {
-    self.emit('error', e);
+  this.parser.on('error', function(err) {
+    self.emit('error', err);
   });
 
   this.parser.on('packet', function(packet) {
     self.emit('packet', packet);
   });
 
+  if (util.isBrowser) {
+    // Web workers
+    this._initWebWorkers();
+  } else {
+    // Child process + pipes
+    this._initChildProcess();
+  }
+
   this._bind();
+  this._listen();
 };
 
 /**
- * Initialize worker. Bind to more events.
+ * Initialize worker (web workers).
+ * @private
+ */
+
+Worker.prototype._initWebWorkers = function _initWebWorkers() {
+  var self = this;
+
+  this.child = new global.Worker('/bcoin-worker.js');
+
+  this.child.onerror = function onerror(err) {
+    self.emit('error', err);
+    self.emit('exit', -1, null);
+  };
+
+  this.child.onmessage = function onmessage(event) {
+    var data;
+    if (typeof event.data !== 'string') {
+      data = event.data.buf;
+      data.__proto__ = Buffer.prototype;
+    } else {
+      data = new Buffer(event.data, 'hex');
+    }
+    self.emit('data', data);
+  };
+
+  this.child.postMessage(JSON.stringify(this.env));
+};
+
+/**
+ * Initialize worker (node.js).
+ * @private
+ */
+
+Worker.prototype._initChildProcess = function _initChildProcess() {
+  var self = this;
+  var file = process.argv[0];
+  var argv = [__dirname + '/worker.js'];
+  var env = util.merge({}, process.env, this.env);
+  var options = { stdio: 'pipe', env: env };
+
+  this.child = cp.spawn(file, argv, options);
+
+  this.child.on('error', function(err) {
+    self.emit('error', err);
+  });
+
+  this.child.on('exit', function(code, signal) {
+    self.emit('exit', code == null ? -1 : code, signal);
+  });
+
+  this.child.on('close', function() {
+    self.emit('exit', -1, null);
+  });
+
+  this.child.stdin.on('error', function(err) {
+    self.emit('error', err);
+  });
+
+  this.child.stdout.on('error', function(err) {
+    self.emit('error', err);
+  });
+
+  this.child.stderr.on('error', function(err) {
+    self.emit('error', err);
+  });
+
+  this.child.stdout.on('data', function(data) {
+    self.emit('data', data);
+  });
+};
+
+/**
+ * Bind to exit listener.
  * @private
  */
 
@@ -521,33 +537,64 @@ Worker.prototype._bind = function _bind() {
       WorkerPool.children.splice(i, 1);
   });
 
-  this.on('packet', function(packet) {
-    switch (packet.cmd) {
-      case packets.types.EVENT:
-        self.emit.apply(self, packet.items);
-        self.emit('event', packet.items);
-        break;
-      case packets.types.LOG:
-        util.log('Worker %d:', self.id);
-        util.log.apply(util, packet.items);
-        break;
-      case packets.types.ERROR:
-        self.emit('error', packet.error);
-        break;
-      case packets.types.ERRORRESULT:
-        self.rejectJob(packet.id, packet.error);
-        break;
-      default:
-        self.resolveJob(packet.id, packet);
-        break;
-    }
-  });
-
   WorkerPool.children.push(this);
 
   WorkerPool._bindExit();
 };
 
+/**
+ * Listen for packets.
+ * @private
+ */
+
+Worker.prototype._listen = function _listen() {
+  var self = this;
+
+  this.on('exit', function() {
+    self.killJobs();
+  });
+
+  this.on('error', function() {
+    self.killJobs();
+  });
+
+  this.on('packet', function(packet) {
+    try {
+      self.handlePacket(packet);
+    } catch (e) {
+      self.emit('error', e);
+    }
+  });
+};
+
+/**
+ * Handle packet.
+ * @private
+ * @param {Packet} packet
+ */
+
+Worker.prototype.handlePacket = function handlePacket(packet) {
+  switch (packet.cmd) {
+    case packets.types.EVENT:
+      this.emit.apply(this, packet.items);
+      this.emit('event', packet.items);
+      break;
+    case packets.types.LOG:
+      util.log('Worker %d:', this.id);
+      util.log.apply(util, packet.items);
+      break;
+    case packets.types.ERROR:
+      this.emit('error', packet.error);
+      break;
+    case packets.types.ERRORRESULT:
+      this.rejectJob(packet.id, packet.error);
+      break;
+    default:
+      this.resolveJob(packet.id, packet);
+      break;
+  }
+};
+
 /**
  * Send data to worker.
  * @param {Buffer} data
@@ -684,6 +731,9 @@ Worker.prototype.killJobs = function killJobs() {
 /**
  * PendingWorker
  * @constructor
+ * @param {Worker} worker
+ * @param {Number} id
+ * @param {Function} callback
  */
 
 function PendingJob(worker, id, callback) {
@@ -693,6 +743,11 @@ function PendingJob(worker, id, callback) {
   this.timer = null;
 }
 
+/**
+ * Start the timer.
+ * @param {Number} timeout
+ */
+
 PendingJob.prototype.start = function start(timeout) {
   var self = this;
 
@@ -704,10 +759,20 @@ PendingJob.prototype.start = function start(timeout) {
   }, timeout);
 };
 
+/**
+ * Destroy the job with an error.
+ */
+
 PendingJob.prototype.destroy = function destroy() {
   this.finish(new Error('Job was destroyed.'));
 };
 
+/**
+ * Complete job with error and result.
+ * @param {Error} err
+ * @param {Object} reject
+ */
+
 PendingJob.prototype.finish = function finish(err, result) {
   var callback = this.callback;