diff --git a/sf-writer/sf_h5_writer.cpp b/sf-writer/sf_h5_writer.cpp
index 794e3f3..8233f89 100644
--- a/sf-writer/sf_h5_writer.cpp
+++ b/sf-writer/sf_h5_writer.cpp
@@ -33,93 +33,89 @@ int main (int argc, char *argv[])
     uint64_t start_pulse_id = (uint64_t) atoll(argv[2]);
     uint64_t stop_pulse_id = (uint64_t) atoll(argv[3]);
 
-//    H5Writer writer(output_file);
-//    writer.create_file();
-
-    size_t n_modules = 32;
-
-    auto metadata_buffer = make_unique<ModuleFrame>();
-    auto image_buffer = make_unique<uint16_t[]>(n_modules*512*1024);
-
-    uint32_t all_modules_ready = 0;
-    for (size_t i=0; i<n_modules; i++) {
-        all_modules_ready |= 1 << i;
-    }
-
-    atomic_uint32_t modules_ready = all_modules_ready;
+    H5Writer writer(output_file);
+    writer.create_file();
 
     auto ctx = zmq_ctx_new();
     zmq_ctx_set (ctx, ZMQ_IO_THREADS, 16);
 
-    vector<thread> threads(n_modules);
-
-    auto read_thread = [&](int module_id) {
-        auto socket = zmq_socket(ctx, ZMQ_PULL);
-
-        int rcvhwm = 100;
-        if (zmq_setsockopt(socket, ZMQ_RCVHWM, &rcvhwm, sizeof(rcvhwm)) != 0)
-            throw runtime_error(strerror (errno));
-
-        int linger = 0;
-        if (zmq_setsockopt(socket, ZMQ_LINGER, &linger, sizeof(linger)) != 0)
-            throw runtime_error(strerror (errno));
-
-        auto ipc_address = "ipc://sf-replay-" + to_string(module_id);
-        if (zmq_bind(socket, ipc_address.c_str()) != 0)
-            throw runtime_error(strerror (errno));
-
-        uint32_t module_mask = 0;
-        module_mask |= 1 << module_id;
-
-        while (true) {
-            if ((modules_ready & module_mask) == 0) {
-                continue;
-            }
-
-            auto n_bytes_metadata = zmq_recv(
-                    socket,
-                    metadata_buffer.get(),
-                    sizeof(ModuleFrame),
-                    0);
-
-            if (n_bytes_metadata != sizeof(ModuleFrame))
-                throw runtime_error(strerror (errno));
-
-            auto image_buffer_offset = 512*1024*module_id;
-            auto n_bytes_image = zmq_recv(
-                    socket,
-                    image_buffer.get() + image_buffer_offset,
-                    512 * 1024 * 2,
-                    0);
-
-            if (n_bytes_image != 512 * 1024 * 2) {
-                throw runtime_error(strerror (errno));
-            }
-
-            modules_ready ^= 1 << module_id;
-        }
-    };
+    size_t n_modules = 32;
+    void* sockets[n_modules];
 
     for (size_t i=0; i<n_modules; i++) {
-        threads.emplace_back(read_thread, i);
+        sockets[i] = zmq_socket(ctx, ZMQ_PULL);
+        int rcvhwm = 100;
+        if (zmq_setsockopt(sockets[i], ZMQ_RCVHWM, &rcvhwm, sizeof(rcvhwm)) != 0) {
+            throw runtime_error(strerror (errno));
+        }
+        int linger = 0;
+        if (zmq_setsockopt(sockets[i], ZMQ_LINGER, &linger, sizeof(linger)) != 0) {
+            throw runtime_error(strerror (errno));
+        }
+
+        stringstream ipc_addr;
+        ipc_addr << "ipc://sf-replay-" << i;
+        auto ipc = ipc_addr.str();
+
+        if (zmq_bind(sockets[i], ipc.c_str()) != 0) {
+            throw runtime_error(strerror (errno));
+        }
     }
 
+
+    auto metadata_buffer = make_unique<ModuleFrame>();
+    auto image_buffer = make_unique<uint16_t[]>(32*512*1024);
+
     int i_write = 0;
     size_t total_ms = 0;
     size_t max_ms = 0;
 
-    auto start_time = chrono::steady_clock::now();
-
     while (true) {
+        uint64_t pulse_id = 0;
 
-        if (modules_ready > 0) {
-            continue;
+        auto start_time = chrono::steady_clock::now();
+
+        for (size_t i=0; i<n_modules; i++) {
+            auto n_bytes_metadata = zmq_recv(
+                    sockets[i],
+                    metadata_buffer.get(),
+                    sizeof(ModuleFrame),
+                    0);
+
+            if (n_bytes_metadata != sizeof(ModuleFrame)) {
+                throw runtime_error(strerror (errno));
+
+            }
+
+            if (i == 0) {
+                pulse_id = metadata_buffer->pulse_id;
+            }
+
+            if (pulse_id != metadata_buffer->pulse_id) {
+                cout << "Module " << i << " pulse " << metadata_buffer->pulse_id;
+                cout << " instead of " << pulse_id << endl;
+            }
+
+            auto n_bytes_image = zmq_recv(
+                    sockets[i],
+                    (image_buffer.get() + (512*1024*i)),
+                    512 * 1024 * 2,
+                    0);
+
+            if (n_bytes_image != 512 * 1024 * 2) {
+                cout << "n_bytes_image " << n_bytes_image << endl;
+                throw runtime_error("Unexpected number of bytes in image.");
+            }
         }
 
+//        writer.write_data("image", i_write, (char*) (image_buffer.get()),
+//                {32*512, 1024}, 32*512*1024*2, "uint16", "little");
         i_write++;
 
         auto end_time = chrono::steady_clock::now();
 
+        // TODO: Some poor statistics.
+
         auto ms_duration = chrono::duration_cast<chrono::milliseconds>(end_time-start_time).count();
         total_ms += ms_duration;
         if (ms_duration > max_ms) {
@@ -127,16 +123,21 @@ int main (int argc, char *argv[])
         }
 
         if (i_write==100) {
-            cout << "avg_ms " << total_ms / 100;
+            cout << "assembly_ms " << total_ms / 100;
             cout << " max_ms " << max_ms << endl;
             i_write = 0;
             total_ms = 0;
             max_ms = 0;
         }
-        start_time = chrono::steady_clock::now();
-
-        modules_ready = all_modules_ready;
     }
 
+    writer.close_file();
+
+    for (size_t i=0; i<n_modules; i++) {
+        zmq_close(sockets[i]);
+    }
+
+    zmq_ctx_destroy(ctx);
+
     return 0;
 }