diff --git a/sf-replay/src/main.cpp b/sf-replay/src/main.cpp
index b7b8ae9..39e432d 100644
--- a/sf-replay/src/main.cpp
+++ b/sf-replay/src/main.cpp
@@ -94,9 +94,9 @@ void sf_replay (
 
 int main (int argc, char *argv[]) {
 
-    if (argc != 6) {
+    if (argc != 7) {
         cout << endl;
-        cout << "Usage: sf_replay [device]";
+        cout << "Usage: sf_replay [ipc_id] [device]";
         cout << " [channel_name] [source_id] [start_pulse_id] [stop_pulse_id]";
         cout << endl;
         cout << "\tdevice: Name of detector." << endl;
@@ -109,14 +109,16 @@ int main (int argc, char *argv[]) {
         exit(-1);
     }
 
-    const string device = string(argv[1]);
-    const string channel_name = string(argv[2]);
-    const auto source_id = (uint16_t) atoi(argv[3]);
-    const auto start_pulse_id = (uint64_t) atoll(argv[4]);
-    const auto stop_pulse_id = (uint64_t) atoll(argv[5]);
+    const string ipc_id = string(argv[1]);
+    const string device = string(argv[2]);
+    const string channel_name = string(argv[3]);
+    const auto source_id = (uint16_t) atoi(argv[4]);
+    const auto start_pulse_id = (uint64_t) atoll(argv[5]);
+    const auto stop_pulse_id = (uint64_t) atoll(argv[6]);
 
+    auto ipc_base = REPLAY_STREAM_IPC_URL + ipc_id;
     stringstream ipc_stream;
-    ipc_stream << REPLAY_STREAM_IPC_URL << (int)source_id;
+    ipc_stream << ipc_base << (int)source_id;
     const auto ipc_address = ipc_stream.str();
 
     auto ctx = zmq_ctx_new();
diff --git a/sf-writer/src/WriterH5Writer.cpp b/sf-writer/src/WriterH5Writer.cpp
index 750d6a6..d7911de 100644
--- a/sf-writer/src/WriterH5Writer.cpp
+++ b/sf-writer/src/WriterH5Writer.cpp
@@ -158,5 +158,5 @@ void WriterH5Writer::write(
             &(metadata->is_good_frame), H5::PredType::NATIVE_UINT8,
             b_m_space, f_m_space);
 
-    current_write_index_++;
+    current_write_index_ += n_images_in_buffer;
 }
diff --git a/sf-writer/src/main.cpp b/sf-writer/src/main.cpp
index f4ceb8f..718703e 100644
--- a/sf-writer/src/main.cpp
+++ b/sf-writer/src/main.cpp
@@ -66,11 +66,12 @@ void receive_replay(
 
 int main (int argc, char *argv[])
 {
-    if (argc != 4) {
+    if (argc != 5) {
         cout << endl;
         cout << "Usage: sf_writer ";
-        cout << " [output_file] [start_pulse_id] [stop_pulse_id]";
+        cout << " [ipc_id] [output_file] [start_pulse_id] [stop_pulse_id]";
         cout << endl;
+        cout << "\tipc_id: Unique identifier for ipc." << endl;
         cout << "\toutput_file: Complete path to the output file." << endl;
         cout << "\tstart_pulse_id: Start pulse_id of retrieval." << endl;
         cout << "\tstop_pulse_id: Stop pulse_id of retrieval." << endl;
@@ -79,9 +80,10 @@ int main (int argc, char *argv[])
         exit(-1);
     }
 
-    string output_file = string(argv[1]);
-    uint64_t start_pulse_id = (uint64_t) atoll(argv[2]);
-    uint64_t stop_pulse_id = (uint64_t) atoll(argv[3]);
+    const string ipc_id = string(argv[1]);
+    string output_file = string(argv[2]);
+    uint64_t start_pulse_id = (uint64_t) atoll(argv[3]);
+    uint64_t stop_pulse_id = (uint64_t) atoll(argv[4]);
 
     size_t n_modules = 32;
 
@@ -92,9 +94,10 @@ int main (int argc, char *argv[])
     auto ctx = zmq_ctx_new();
     zmq_ctx_set (ctx, ZMQ_IO_THREADS, WRITER_ZMQ_IO_THREADS);
 
+    auto ipc_base = REPLAY_STREAM_IPC_URL + ipc_id;
     thread replay_receive_thread(receive_replay,
-            ctx, REPLAY_STREAM_IPC_URL, n_modules,
-            ref(queue), start_pulse_id, stop_pulse_id);
+                                 ctx, ipc_base, n_modules,
+                                 ref(queue), start_pulse_id, stop_pulse_id);
 
     size_t n_frames = stop_pulse_id - start_pulse_id + 1;
     WriterH5Writer writer(output_file, n_frames, n_modules);