diff --git a/gui/src/main.cpp b/gui/src/main.cpp
index faedc7c..36ca884 100644
--- a/gui/src/main.cpp
+++ b/gui/src/main.cpp
@@ -76,7 +76,7 @@ int main(int argc, char *argv[])
 
 		chiaki_connect_video_profile_preset(&connect_info.video_profile,
 				CHIAKI_VIDEO_RESOLUTION_PRESET_720p,
-				CHIAKI_VIDEO_FPS_PRESET_60);
+				CHIAKI_VIDEO_FPS_PRESET_30);
 
 		if(connect_info.registkey.isEmpty() || connect_info.ostype.isEmpty() || connect_info.auth.isEmpty() || connect_info.morning.isEmpty() || connect_info.did.isEmpty())
 			parser.showHelp(1);
diff --git a/lib/include/chiaki/senkusha.h b/lib/include/chiaki/senkusha.h
index 0e3e5ec..731c81c 100644
--- a/lib/include/chiaki/senkusha.h
+++ b/lib/include/chiaki/senkusha.h
@@ -36,6 +36,7 @@ typedef struct senkusha_t
 	bool state_finished;
 	bool state_failed;
 	bool should_stop;
+	ChiakiSeqNum32 data_ack_seq_num_expected;
 
 	/**
 	 * signaled on change of state_finished or should_stop
diff --git a/lib/include/chiaki/takion.h b/lib/include/chiaki/takion.h
index b64528e..727a2b4 100644
--- a/lib/include/chiaki/takion.h
+++ b/lib/include/chiaki/takion.h
@@ -80,6 +80,7 @@ typedef enum {
 	CHIAKI_TAKION_EVENT_TYPE_CONNECTED,
 	CHIAKI_TAKION_EVENT_TYPE_DISCONNECT,
 	CHIAKI_TAKION_EVENT_TYPE_DATA,
+	CHIAKI_TAKION_EVENT_TYPE_DATA_ACK,
 	CHIAKI_TAKION_EVENT_TYPE_AV
 } ChiakiTakionEventType;
 
@@ -95,6 +96,11 @@ typedef struct chiaki_takion_event_t
 			size_t buf_size;
 		} data;
 
+		struct
+		{
+			ChiakiSeqNum32 seq_num;
+		} data_ack;
+
 		ChiakiTakionAVPacket *av;
 	};
 } ChiakiTakionEvent;
@@ -198,8 +204,10 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send(ChiakiTakion *takion, uint8_t *
 
 /**
  * Thread-safe while Takion is running.
+ *
+ * @param optional pointer to write the sequence number of the sent package to
  */
-CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_message_data(ChiakiTakion *takion, uint8_t chunk_flags, uint16_t channel, uint8_t *buf, size_t buf_size);
+CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_message_data(ChiakiTakion *takion, uint8_t chunk_flags, uint16_t channel, uint8_t *buf, size_t buf_size, ChiakiSeqNum32 *seq_num);
 
 /**
  * Thread-safe while Takion is running.
diff --git a/lib/include/chiaki/takionsendbuffer.h b/lib/include/chiaki/takionsendbuffer.h
index bdf6ffd..3ecff3a 100644
--- a/lib/include/chiaki/takionsendbuffer.h
+++ b/lib/include/chiaki/takionsendbuffer.h
@@ -63,7 +63,11 @@ CHIAKI_EXPORT void chiaki_takion_send_buffer_fini(ChiakiTakionSendBuffer *send_b
  * On error, buf is freed immediately.
  */
 CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_buffer_push(ChiakiTakionSendBuffer *send_buffer, ChiakiSeqNum32 seq_num, uint8_t *buf, size_t buf_size);
-CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_buffer_ack(ChiakiTakionSendBuffer *send_buffer, ChiakiSeqNum32 seq_num);
+
+/**
+ * @param acked_seq_nums optional array of size of at least send_buffer->packets_size where acked seq nums will be stored
+ */
+CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_buffer_ack(ChiakiTakionSendBuffer *send_buffer, ChiakiSeqNum32 seq_num, ChiakiSeqNum32 *acked_seq_nums, size_t *acked_seq_nums_count);
 
 #ifdef __cplusplus
 }
diff --git a/lib/src/senkusha.c b/lib/src/senkusha.c
index 6f1d637..539232e 100644
--- a/lib/src/senkusha.c
+++ b/lib/src/senkusha.c
@@ -28,22 +28,30 @@
 #include <pb_encode.h>
 #include <pb_decode.h>
 #include <pb.h>
+#include <chiaki/takion.h>
 
 
 #define SENKUSHA_PORT 9297
 
 #define EXPECT_TIMEOUT_MS 5000
 
+#define SENKUSHA_PING_COUNT_DEFAULT 10
+
 typedef enum {
 	STATE_IDLE,
 	STATE_TAKION_CONNECT,
-	STATE_EXPECT_BANG
+	STATE_EXPECT_BANG,
+	STATE_EXPECT_DATA_ACK,
+	STATE_EXPECT_PONG,
 } SenkushaState;
 
+static ChiakiErrorCode senkusha_run_ping_test(ChiakiSenkusha *senkusha, uint32_t ping_count);
 static void senkusha_takion_cb(ChiakiTakionEvent *event, void *user);
 static void senkusha_takion_data(ChiakiSenkusha *senkusha, ChiakiTakionMessageDataType data_type, uint8_t *buf, size_t buf_size);
+static void senkusha_takion_data_ack(ChiakiSenkusha *senkusha, ChiakiSeqNum32 seq_num);
 static ChiakiErrorCode senkusha_send_big(ChiakiSenkusha *senkusha);
 static ChiakiErrorCode senkusha_send_disconnect(ChiakiSenkusha *senkusha);
+static ChiakiErrorCode senkusha_send_echo_command(ChiakiSenkusha *senkusha, bool enable);
 
 CHIAKI_EXPORT ChiakiErrorCode chiaki_senkusha_init(ChiakiSenkusha *senkusha, ChiakiSession *session)
 {
@@ -178,7 +186,7 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_senkusha_run(ChiakiSenkusha *senkusha)
 
 	CHIAKI_LOGI(session->log, "Senkusha successfully received bang");
 
-	// TODO: Do the actual tests
+	senkusha_run_ping_test(senkusha, SENKUSHA_PING_COUNT_DEFAULT);
 
 	CHIAKI_LOGI(session->log, "Senkusha is disconnecting");
 
@@ -193,6 +201,33 @@ quit:
 	return err;
 }
 
+static ChiakiErrorCode senkusha_run_ping_test(ChiakiSenkusha *senkusha, uint32_t ping_count)
+{
+	CHIAKI_LOGI(senkusha->log, "Senkusha Ping Test with count %u starting", (unsigned int)ping_count);
+
+	ChiakiErrorCode err = senkusha_send_echo_command(senkusha, true);
+	if(err != CHIAKI_ERR_SUCCESS)
+	{
+		CHIAKI_LOGE(senkusha->log, "Senkusha Ping Test failed because sending echo command (true) failed");
+		return err;
+	}
+
+	CHIAKI_LOGI(senkusha->log, "Senkusha enabled echo");
+
+	// TODO: do test
+
+	err = senkusha_send_echo_command(senkusha, false);
+	if(err != CHIAKI_ERR_SUCCESS)
+	{
+		CHIAKI_LOGE(senkusha->log, "Senkusha Ping Test failed because sending echo command (false) failed");
+		return err;
+	}
+
+	CHIAKI_LOGI(senkusha->log, "Senkusha disabled echo");
+
+	return CHIAKI_ERR_SUCCESS;
+}
+
 static void senkusha_takion_cb(ChiakiTakionEvent *event, void *user)
 {
 	ChiakiSenkusha *senkusha = user;
@@ -212,6 +247,9 @@ static void senkusha_takion_cb(ChiakiTakionEvent *event, void *user)
 		case CHIAKI_TAKION_EVENT_TYPE_DATA:
 			senkusha_takion_data(senkusha, event->data.data_type, event->data.buf, event->data.buf_size);
 			break;
+		case CHIAKI_TAKION_EVENT_TYPE_DATA_ACK:
+			senkusha_takion_data_ack(senkusha, event->data_ack.seq_num);
+			break;
 		default:
 			break;
 	}
@@ -249,6 +287,19 @@ static void senkusha_takion_data(ChiakiSenkusha *senkusha, ChiakiTakionMessageDa
 	chiaki_mutex_unlock(&senkusha->state_mutex);
 }
 
+static void senkusha_takion_data_ack(ChiakiSenkusha *senkusha, ChiakiSeqNum32 seq_num)
+{
+	chiaki_mutex_lock(&senkusha->state_mutex);
+	if(senkusha->state == STATE_EXPECT_DATA_ACK && senkusha->data_ack_seq_num_expected == seq_num)
+	{
+		senkusha->state_finished = true;
+		chiaki_mutex_unlock(&senkusha->state_mutex);
+		chiaki_cond_signal(&senkusha->state_cond);
+	}
+	else
+		chiaki_mutex_unlock(&senkusha->state_mutex);
+}
+
 static ChiakiErrorCode senkusha_send_big(ChiakiSenkusha *senkusha)
 {
 	tkproto_TakionMessage msg;
@@ -276,7 +327,7 @@ static ChiakiErrorCode senkusha_send_big(ChiakiSenkusha *senkusha)
 	}
 
 	buf_size = stream.bytes_written;
-	ChiakiErrorCode err = chiaki_takion_send_message_data(&senkusha->takion, 1, 1, buf, buf_size);
+	ChiakiErrorCode err = chiaki_takion_send_message_data(&senkusha->takion, 1, 1, buf, buf_size, NULL);
 
 	return err;
 }
@@ -303,9 +354,57 @@ static ChiakiErrorCode senkusha_send_disconnect(ChiakiSenkusha *senkusha)
 	}
 
 	buf_size = stream.bytes_written;
-	ChiakiErrorCode err = chiaki_takion_send_message_data(&senkusha->takion, 1, 1, buf, buf_size);
+	ChiakiErrorCode err = chiaki_takion_send_message_data(&senkusha->takion, 1, 1, buf, buf_size, NULL);
 
 	return err;
 }
 
+static ChiakiErrorCode senkusha_send_echo_command(ChiakiSenkusha *senkusha, bool enable)
+{
+	tkproto_TakionMessage msg;
+	memset(&msg, 0, sizeof(msg));
 
+	msg.type = tkproto_TakionMessage_PayloadType_SENKUSHA;
+	msg.has_senkusha_payload = true;
+	msg.senkusha_payload.command = tkproto_SenkushaPayload_Command_ECHO_COMMAND;
+	msg.senkusha_payload.has_echo_command = true;
+	msg.senkusha_payload.echo_command.state = enable;
+
+	uint8_t buf[0x10];
+	size_t buf_size;
+
+	pb_ostream_t stream = pb_ostream_from_buffer(buf, sizeof(buf));
+	bool pbr = pb_encode(&stream, tkproto_TakionMessage_fields, &msg);
+	if(!pbr)
+	{
+		CHIAKI_LOGE(senkusha->log, "Senkusha echo command protobuf encoding failed");
+		return CHIAKI_ERR_UNKNOWN;
+	}
+
+	buf_size = stream.bytes_written;
+	senkusha->state = STATE_EXPECT_DATA_ACK;
+	senkusha->state_finished = false;
+	senkusha->state_failed = false;
+	ChiakiErrorCode err = chiaki_takion_send_message_data(&senkusha->takion, 1, 1, buf, buf_size, &senkusha->data_ack_seq_num_expected);
+	if(err != CHIAKI_ERR_SUCCESS)
+	{
+		CHIAKI_LOGE(senkusha->log, "Senkusha failed to send echo command");
+		return err;
+	}
+
+	err = chiaki_cond_timedwait_pred(&senkusha->state_cond, &senkusha->state_mutex, EXPECT_TIMEOUT_MS, state_finished_cond_check, senkusha);
+	assert(err == CHIAKI_ERR_SUCCESS || err == CHIAKI_ERR_TIMEOUT);
+
+	if(!senkusha->state_finished)
+	{
+		if(err == CHIAKI_ERR_TIMEOUT)
+			CHIAKI_LOGE(senkusha->log, "Senkusha data ack for echo command receive timeout");
+
+		if(senkusha->should_stop)
+			err = CHIAKI_ERR_CANCELED;
+		else
+			CHIAKI_LOGE(senkusha->log, "Senkusha failed to receive data ack for echo command");
+	}
+
+	return err;
+}
diff --git a/lib/src/session.c b/lib/src/session.c
index 5044a9b..4ca70cc 100644
--- a/lib/src/session.c
+++ b/lib/src/session.c
@@ -257,7 +257,7 @@ static bool session_check_state_pred(void *user)
 		|| session->ctrl_session_id_received;
 }
 
-//#define ENABLE_SENKUSHA
+#define ENABLE_SENKUSHA
 
 static void *session_thread_func(void *arg)
 {
diff --git a/lib/src/streamconnection.c b/lib/src/streamconnection.c
index 4f6c7fb..849fe01 100644
--- a/lib/src/streamconnection.c
+++ b/lib/src/streamconnection.c
@@ -728,7 +728,7 @@ static ChiakiErrorCode stream_connection_send_big(ChiakiStreamConnection *stream
 	}
 
 	buf_size = stream.bytes_written;
-	err = chiaki_takion_send_message_data(&stream_connection->takion, 1, 1, buf, buf_size);
+	err = chiaki_takion_send_message_data(&stream_connection->takion, 1, 1, buf, buf_size, NULL);
 
 	return err;
 }
@@ -751,7 +751,7 @@ static ChiakiErrorCode stream_connection_send_streaminfo_ack(ChiakiStreamConnect
 	}
 
 	buf_size = stream.bytes_written;
-	return chiaki_takion_send_message_data(&stream_connection->takion, 1, 9, buf, buf_size);
+	return chiaki_takion_send_message_data(&stream_connection->takion, 1, 9, buf, buf_size, NULL);
 }
 
 static ChiakiErrorCode stream_connection_send_disconnect(ChiakiStreamConnection *stream_connection)
@@ -778,7 +778,7 @@ static ChiakiErrorCode stream_connection_send_disconnect(ChiakiStreamConnection
 	CHIAKI_LOGI(stream_connection->log, "StreamConnection sending Disconnect");
 
 	buf_size = stream.bytes_written;
-	ChiakiErrorCode err = chiaki_takion_send_message_data(&stream_connection->takion, 1, 1, buf, buf_size);
+	ChiakiErrorCode err = chiaki_takion_send_message_data(&stream_connection->takion, 1, 1, buf, buf_size, NULL);
 
 	return err;
 }
@@ -810,7 +810,7 @@ static ChiakiErrorCode stream_connection_send_heartbeat(ChiakiStreamConnection *
 		return CHIAKI_ERR_UNKNOWN;
 	}
 
-	return chiaki_takion_send_message_data(&stream_connection->takion, 1, 1, buf, stream.bytes_written);
+	return chiaki_takion_send_message_data(&stream_connection->takion, 1, 1, buf, stream.bytes_written, NULL);
 }
 
 CHIAKI_EXPORT ChiakiErrorCode stream_connection_send_corrupt_frame(ChiakiStreamConnection *stream_connection, ChiakiSeqNum16 start, ChiakiSeqNum16 end)
@@ -832,5 +832,5 @@ CHIAKI_EXPORT ChiakiErrorCode stream_connection_send_corrupt_frame(ChiakiStreamC
 	}
 
 	CHIAKI_LOGD(stream_connection->log, "StreamConnection reporting corrupt frame(s) from %u to %u", (unsigned int)start, (unsigned int)end);
-	return chiaki_takion_send_message_data(&stream_connection->takion, 1, 2, buf, stream.bytes_written);
+	return chiaki_takion_send_message_data(&stream_connection->takion, 1, 2, buf, stream.bytes_written, NULL);
 }
diff --git a/lib/src/takion.c b/lib/src/takion.c
index 9b81272..2567bfb 100644
--- a/lib/src/takion.c
+++ b/lib/src/takion.c
@@ -349,7 +349,7 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send(ChiakiTakion *takion, uint8_t *
 	return chiaki_takion_send_raw(takion, buf, buf_size);
 }
 
-CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_message_data(ChiakiTakion *takion, uint8_t chunk_flags, uint16_t channel, uint8_t *buf, size_t buf_size)
+CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_message_data(ChiakiTakion *takion, uint8_t chunk_flags, uint16_t channel, uint8_t *buf, size_t buf_size, ChiakiSeqNum32 *seq_num)
 {
 	// TODO: can we make this more memory-efficient?
 	// TODO: split packet if necessary?
@@ -372,10 +372,10 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_message_data(ChiakiTakion *taki
 	err = chiaki_mutex_lock(&takion->seq_num_local_mutex);
 	if(err != CHIAKI_ERR_SUCCESS)
 		return err;
-	ChiakiSeqNum32 seq_num = takion->seq_num_local++;
+	ChiakiSeqNum32 seq_num_val = takion->seq_num_local++;
 	chiaki_mutex_unlock(&takion->seq_num_local_mutex);
 
-	*((uint32_t *)(msg_payload + 0)) = htonl(seq_num);
+	*((uint32_t *)(msg_payload + 0)) = htonl(seq_num_val);
 	*((uint16_t *)(msg_payload + 4)) = htons(channel);
 	*((uint16_t *)(msg_payload + 6)) = 0;
 	*(msg_payload + 8) = 0;
@@ -389,7 +389,10 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_message_data(ChiakiTakion *taki
 		return err;
 	}
 
-	chiaki_takion_send_buffer_push(&takion->send_buffer, seq_num, packet_buf, packet_size);
+	chiaki_takion_send_buffer_push(&takion->send_buffer, seq_num_val, packet_buf, packet_size);
+
+	if(seq_num)
+		*seq_num = seq_num_val;
 
 	return err;
 }
@@ -606,6 +609,7 @@ static void *takion_thread_func(void *user)
 
 	chiaki_reorder_queue_set_drop_cb(&takion->data_queue, takion_data_drop, takion);
 
+	// The send buffer size MUST be consistent with the acked seqnums array size in takion_handle_packet_message_data_ack()
 	if(chiaki_takion_send_buffer_init(&takion->send_buffer, takion, TAKION_SEND_BUFFER_SIZE) != CHIAKI_ERR_SUCCESS)
 		goto error_reoder_queue;
 
@@ -939,8 +943,20 @@ static void takion_handle_packet_message_data_ack(ChiakiTakion *takion, uint8_t
 	if(dup_tsns_count != 0)
 		CHIAKI_LOGW(takion->log, "Takion received data ack with nonzero dup_tsns_count %#x", dup_tsns_count);
 
-	//CHIAKI_LOGD(takion->log, "Takion received data ack with seq_num = %#x, something = %#x, size_or_something = %#x, zero = %#x", seq_num, something, size_internal, zero);
-	chiaki_takion_send_buffer_ack(&takion->send_buffer, cumulative_seq_num);
+	CHIAKI_LOGV(takion->log, "Takion received data ack with cumulative_seq_num = %#x, a_rwnd = %#x, gap_ack_blocks_count = %#x, dup_tsns_count = %#x",
+			cumulative_seq_num, a_rwnd, gap_ack_blocks_count, dup_tsns_count);
+
+	ChiakiSeqNum32 acked_seq_nums[TAKION_SEND_BUFFER_SIZE];
+	size_t acked_seq_nums_count = 0;
+	chiaki_takion_send_buffer_ack(&takion->send_buffer, cumulative_seq_num, acked_seq_nums, &acked_seq_nums_count);
+
+	for(size_t i=0; i<acked_seq_nums_count; i++)
+	{
+		ChiakiTakionEvent event = { 0 };
+		event.type = CHIAKI_TAKION_EVENT_TYPE_DATA_ACK;
+		event.data_ack.seq_num = acked_seq_nums[i];
+		takion->cb(&event, takion->cb_user);
+	}
 }
 
 /**
diff --git a/lib/src/takionsendbuffer.c b/lib/src/takionsendbuffer.c
index 90086e6..0532c75 100644
--- a/lib/src/takionsendbuffer.c
+++ b/lib/src/takionsendbuffer.c
@@ -144,12 +144,15 @@ beach:
 	return err;
 }
 
-CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_buffer_ack(ChiakiTakionSendBuffer *send_buffer, ChiakiSeqNum32 seq_num)
+CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_buffer_ack(ChiakiTakionSendBuffer *send_buffer, ChiakiSeqNum32 seq_num, ChiakiSeqNum32 *acked_seq_nums, size_t *acked_seq_nums_count)
 {
 	ChiakiErrorCode err = chiaki_mutex_lock(&send_buffer->mutex);
 	if(err != CHIAKI_ERR_SUCCESS)
 		return err;
 
+	if(acked_seq_nums_count)
+		*acked_seq_nums_count = 0;
+
 	size_t i;
 	size_t shift = 0; // amount to shift back
 	size_t shift_start = SIZE_MAX;
@@ -157,6 +160,9 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_takion_send_buffer_ack(ChiakiTakionSendBuff
 	{
 		if(send_buffer->packets[i].seq_num == seq_num || chiaki_seq_num_32_lt(send_buffer->packets[i].seq_num, seq_num))
 		{
+			if(acked_seq_nums)
+				acked_seq_nums[(*acked_seq_nums_count)++] = send_buffer->packets[i].seq_num;
+
 			free(send_buffer->packets[i].buf);
 			if(shift_start == SIZE_MAX)
 			{