diff --git a/fastboot/constants.h b/fastboot/constants.h
new file mode 100644
index 0000000..5e7e955
--- /dev/null
+++ b/fastboot/constants.h
@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#define FB_CMD_GETVAR "getvar"
+#define FB_CMD_DOWNLOAD "download"
+#define FB_CMD_UPLOAD "upload"
+#define FB_CMD_VERIFY "verify"
+#define FB_CMD_FLASH "flash"
+#define FB_CMD_ERASE "erase"
+#define FB_CMD_BOOT "boot"
+#define FB_CMD_SET_ACTIVE "set_active"
+#define FB_CMD_CONTINUE "continue"
+#define FB_CMD_REBOOT "reboot"
+#define FB_CMD_SHUTDOWN "shutdown"
+#define FB_CMD_REBOOT_BOOTLOADER "reboot-bootloader"
+#define FB_CMD_POWERDOWN "powerdown"
+
+#define RESPONSE_OKAY "OKAY"
+#define RESPONSE_FAIL "FAIL"
+#define RESPONSE_DATA "DATA"
+#define RESPONSE_INFO "INFO"
+
+#define FB_COMMAND_SZ 64
+#define FB_RESPONSE_SZ 64
+
+#define FB_VAR_VERSION "version"
+#define FB_VAR_VERSION_BOOTLOADER "version-bootloader"
+#define FB_VAR_VERSION_BASEBAND "version-baseband"
+#define FB_VAR_PRODUCT "product"
+#define FB_VAR_SERIALNO "serialno"
+#define FB_VAR_SECURE "secure"
+#define FB_VAR_UNLOCKED "unlocked"
+#define FB_VAR_CURRENT_SLOT "current-slot"
+#define FB_VAR_MAX_DOWNLOAD_SIZE "max-download-size"
+#define FB_VAR_HAS_SLOT "has-slot"
+#define FB_VAR_SLOT_COUNT "slot-count"
+#define FB_VAR_PARTITION_SIZE "partition-size"
diff --git a/fastboot/engine.cpp b/fastboot/engine.cpp
index f271d09..1087573 100644
--- a/fastboot/engine.cpp
+++ b/fastboot/engine.cpp
@@ -42,6 +42,7 @@
 
 #include <android-base/stringprintf.h>
 
+#include "constants.h"
 #include "transport.h"
 
 enum Op {
@@ -79,7 +80,7 @@
 static std::vector<std::unique_ptr<Action>> action_list;
 
 bool fb_getvar(Transport* transport, const std::string& key, std::string* value) {
-    std::string cmd = "getvar:" + key;
+    std::string cmd = FB_CMD_GETVAR ":" + key;
 
     char buf[FB_RESPONSE_SZ + 1];
     memset(buf, 0, sizeof(buf));
@@ -110,12 +111,12 @@
 }
 
 void fb_set_active(const std::string& slot) {
-    Action& a = queue_action(OP_COMMAND, "set_active:" + slot);
+    Action& a = queue_action(OP_COMMAND, FB_CMD_SET_ACTIVE ":" + slot);
     a.msg = "Setting current slot to '" + slot + "'";
 }
 
 void fb_queue_erase(const std::string& partition) {
-    Action& a = queue_action(OP_COMMAND, "erase:" + partition);
+    Action& a = queue_action(OP_COMMAND, FB_CMD_ERASE ":" + partition);
     a.msg = "Erasing '" + partition + "'";
 }
 
@@ -125,7 +126,7 @@
     a.size = sz;
     a.msg = android::base::StringPrintf("Sending '%s' (%u KB)", partition.c_str(), sz / 1024);
 
-    Action& b = queue_action(OP_COMMAND, "flash:" + partition);
+    Action& b = queue_action(OP_COMMAND, FB_CMD_FLASH ":" + partition);
     b.msg = "Writing '" + partition + "'";
 }
 
@@ -135,7 +136,7 @@
     a.size = sz;
     a.msg = android::base::StringPrintf("Sending '%s' (%u KB)", partition.c_str(), sz / 1024);
 
-    Action& b = queue_action(OP_COMMAND, "flash:" + partition);
+    Action& b = queue_action(OP_COMMAND, FB_CMD_FLASH ":" + partition);
     b.msg = "Writing '" + partition + "'";
 }
 
@@ -147,7 +148,7 @@
     a.msg = android::base::StringPrintf("Sending sparse '%s' %zu/%zu (%u KB)", partition.c_str(),
                                         current, total, sz / 1024);
 
-    Action& b = queue_action(OP_COMMAND, "flash:" + partition);
+    Action& b = queue_action(OP_COMMAND, FB_CMD_FLASH ":" + partition);
     b.msg = android::base::StringPrintf("Writing sparse '%s' %zu/%zu", partition.c_str(), current,
                                         total);
 }
@@ -223,7 +224,7 @@
 
 void fb_queue_require(const std::string& product, const std::string& var, bool invert,
                       size_t nvalues, const char** values) {
-    Action& a = queue_action(OP_QUERY, "getvar:" + var);
+    Action& a = queue_action(OP_QUERY, FB_CMD_GETVAR ":" + var);
     a.product = product;
     a.data = values;
     a.size = nvalues;
@@ -243,7 +244,7 @@
 }
 
 void fb_queue_display(const std::string& label, const std::string& var) {
-    Action& a = queue_action(OP_QUERY, "getvar:" + var);
+    Action& a = queue_action(OP_QUERY, FB_CMD_GETVAR ":" + var);
     a.data = xstrdup(label.c_str());
     a.func = cb_display;
 }
@@ -258,7 +259,7 @@
 }
 
 void fb_queue_query_save(const std::string& var, char* dest, uint32_t dest_size) {
-    Action& a = queue_action(OP_QUERY, "getvar:" + var);
+    Action& a = queue_action(OP_QUERY, FB_CMD_GETVAR ":" + var);
     a.data = dest;
     a.size = dest_size;
     a.func = cb_save;
@@ -270,7 +271,7 @@
 }
 
 void fb_queue_reboot() {
-    Action& a = queue_action(OP_COMMAND, "reboot");
+    Action& a = queue_action(OP_COMMAND, FB_CMD_REBOOT);
     a.func = cb_do_nothing;
     a.msg = "Rebooting";
 }
diff --git a/fastboot/fastboot.h b/fastboot/fastboot.h
index 50c70f3..a93c0ac 100644
--- a/fastboot/fastboot.h
+++ b/fastboot/fastboot.h
@@ -35,6 +35,8 @@
 
 #include <bootimg.h>
 
+#include "constants.h"
+
 class Transport;
 struct sparse_file;
 
@@ -47,9 +49,6 @@
 int64_t fb_upload_data(Transport* transport, const char* outfile);
 const std::string fb_get_error();
 
-#define FB_COMMAND_SZ 64
-#define FB_RESPONSE_SZ 64
-
 /* engine.c - high level command queue engine */
 bool fb_getvar(Transport* transport, const std::string& key, std::string* value);
 void fb_queue_flash(const std::string& partition, void* data, uint32_t sz);
diff --git a/fastboot/protocol.cpp b/fastboot/protocol.cpp
index fda6f5d..e625095 100644
--- a/fastboot/protocol.cpp
+++ b/fastboot/protocol.cpp
@@ -44,6 +44,7 @@
 #include <sparse/sparse.h>
 #include <utils/FileMap.h>
 
+#include "constants.h"
 #include "fastboot.h"
 #include "transport.h"
 
@@ -68,39 +69,39 @@
         }
         status[r] = 0;
 
-        if (r < 4) {
+        if (static_cast<size_t>(r) < strlen(RESPONSE_OKAY)) {
             g_error = android::base::StringPrintf("status malformed (%d bytes)", r);
             transport->Close();
             return -1;
         }
 
-        if (!memcmp(status, "INFO", 4)) {
-            verbose("received INFO \"%s\"", status + 4);
-            fprintf(stderr, "(bootloader) %s\n", status + 4);
+        if (!memcmp(status, RESPONSE_INFO, strlen(RESPONSE_INFO))) {
+            verbose("received INFO \"%s\"", status + strlen(RESPONSE_INFO));
+            fprintf(stderr, "(bootloader) %s\n", status + strlen(RESPONSE_INFO));
             continue;
         }
 
-        if (!memcmp(status, "OKAY", 4)) {
-            verbose("received OKAY \"%s\"", status + 4);
+        if (!memcmp(status, RESPONSE_OKAY, strlen(RESPONSE_OKAY))) {
+            verbose("received OKAY \"%s\"", status + strlen(RESPONSE_OKAY));
             if (response) {
-                strcpy(response, status + 4);
+                strcpy(response, status + strlen(RESPONSE_OKAY));
             }
             return 0;
         }
 
-        if (!memcmp(status, "FAIL", 4)) {
-            verbose("received FAIL \"%s\"", status + 4);
-            if (r > 4) {
-                g_error = android::base::StringPrintf("remote: %s", status + 4);
+        if (!memcmp(status, RESPONSE_FAIL, strlen(RESPONSE_FAIL))) {
+            verbose("received FAIL \"%s\"", status + strlen(RESPONSE_FAIL));
+            if (static_cast<size_t>(r) > strlen(RESPONSE_FAIL)) {
+                g_error = android::base::StringPrintf("remote: %s", status + strlen(RESPONSE_FAIL));
             } else {
                 g_error = "remote failure";
             }
             return -1;
         }
 
-        if (!memcmp(status, "DATA", 4) && size > 0){
-            verbose("received DATA %s", status + 4);
-            uint32_t dsize = strtol(status + 4, 0, 16);
+        if (!memcmp(status, RESPONSE_DATA, strlen(RESPONSE_DATA)) && size > 0){
+            verbose("received DATA %s", status + strlen(RESPONSE_DATA));
+            uint32_t dsize = strtol(status + strlen(RESPONSE_DATA), 0, 16);
             if (dsize > size) {
                 g_error = android::base::StringPrintf("data size too large (%d)", dsize);
                 transport->Close();
@@ -247,18 +248,21 @@
 }
 
 int64_t fb_download_data(Transport* transport, const void* data, uint32_t size) {
-    std::string cmd(android::base::StringPrintf("download:%08x", size));
+    std::string cmd(android::base::StringPrintf(
+                FB_CMD_DOWNLOAD ":" "%08x", size));
     return _command_send(transport, cmd.c_str(), data, size, 0) < 0 ? -1 : 0;
 }
 
 int64_t fb_download_data_fd(Transport* transport, int fd, uint32_t size) {
-    std::string cmd(android::base::StringPrintf("download:%08x", size));
+    std::string cmd(android::base::StringPrintf(
+                FB_CMD_DOWNLOAD ":" "%08x", size));
     return _command_send_fd(transport, cmd.c_str(), fd, size, 0) < 0 ? -1 : 0;
 }
 
 int64_t fb_upload_data(Transport* transport, const char* outfile) {
     // positive return value is the upload size sent by the device
-    int64_t r = _command_start(transport, "upload", std::numeric_limits<int32_t>::max(), nullptr);
+    int64_t r = _command_start(transport, FB_CMD_UPLOAD,
+            std::numeric_limits<int32_t>::max(), nullptr);
     if (r <= 0) {
         g_error = android::base::StringPrintf("command start failed (%s)", strerror(errno));
         return r;
@@ -345,7 +349,8 @@
         return -1;
     }
 
-    std::string cmd(android::base::StringPrintf("download:%08" PRIx64, size));
+    std::string cmd(android::base::StringPrintf(
+                FB_CMD_DOWNLOAD ":" "%08" PRIx64, size));
     int r = _command_start(transport, cmd, size, 0);
     if (r < 0) {
         return -1;