diff --git a/src/monitor/diff-test/diff-test.c b/src/monitor/diff-test/diff-test.c
index 30986ff7d2e6a0e95927949ac13b4983c61efe4f..d42f1501500f2d50ff18d2a15d091a089bbd3680 100644
--- a/src/monitor/diff-test/diff-test.c
+++ b/src/monitor/diff-test/diff-test.c
@@ -45,7 +45,7 @@ void difftest_skip_dut(int nr_ref, int nr_dut) {
 bool isa_difftest_checkregs(CPU_state *ref_r, vaddr_t pc);
 void isa_difftest_attach(void);
 
-void init_difftest(char *ref_so_file, long img_size) {
+void init_difftest(char *ref_so_file, long img_size, int port) {
 #ifndef DIFF_TEST
   return;
 #endif
@@ -68,7 +68,7 @@ void init_difftest(char *ref_so_file, long img_size) {
   ref_difftest_exec = dlsym(handle, "difftest_exec");
   assert(ref_difftest_exec);
 
-  void (*ref_difftest_init)(void) = dlsym(handle, "difftest_init");
+  void (*ref_difftest_init)(int) = dlsym(handle, "difftest_init");
   assert(ref_difftest_init);
 
   Log("Differential testing: \33[1;32m%s\33[0m", "ON");
@@ -76,7 +76,7 @@ void init_difftest(char *ref_so_file, long img_size) {
       "This will help you a lot for debugging, but also significantly reduce the performance. "
       "If it is not necessary, you can turn it off in include/common.h.", ref_so_file);
 
-  ref_difftest_init();
+  ref_difftest_init(port);
   ref_difftest_memcpy_from_dut(PC_START, guest_to_host(IMAGE_START), img_size);
   char *mainargs = guest_to_host(0);
   ref_difftest_memcpy_from_dut(PC_START - IMAGE_START, mainargs, strlen(mainargs) + 1);
diff --git a/src/monitor/monitor.c b/src/monitor/monitor.c
index f3ba2fda40eb3b756ed41ba4ea9681fd0f023431..3bf47e8ad4fcc4a681d6ac16ae0c4b2226a7125d 100644
--- a/src/monitor/monitor.c
+++ b/src/monitor/monitor.c
@@ -7,13 +7,14 @@ void init_isa();
 void init_regex();
 void init_wp_pool();
 void init_device();
-void init_difftest(char *ref_so_file, long img_size);
+void init_difftest(char *ref_so_file, long img_size, int port);
 
 static char *mainargs = "";
 static char *log_file = NULL;
 static char *diff_so_file = NULL;
 static char *img_file = NULL;
 static int is_batch_mode = false;
+static int difftest_port = 1234;
 
 static inline void welcome() {
 #ifdef DEBUG
@@ -64,10 +65,11 @@ static inline long load_img() {
 
 static inline void parse_args(int argc, char *argv[]) {
   int o;
-  while ( (o = getopt(argc, argv, "-bl:d:a:")) != -1) {
+  while ( (o = getopt(argc, argv, "-bl:d:a:p:")) != -1) {
     switch (o) {
       case 'b': is_batch_mode = true; break;
       case 'a': mainargs = optarg; break;
+      case 'p': sscanf(optarg, "%d", &difftest_port); break;
       case 'l': log_file = optarg; break;
       case 'd': diff_so_file = optarg; break;
       case 1:
@@ -105,7 +107,7 @@ int init_monitor(int argc, char *argv[]) {
   init_device();
 
   /* Initialize differential testing. */
-  init_difftest(diff_so_file, img_size);
+  init_difftest(diff_so_file, img_size, difftest_port);
 
   /* Display welcome message. */
   welcome();
diff --git a/tools/qemu-diff/src/diff-test.c b/tools/qemu-diff/src/diff-test.c
index 0cc086437d902cacdb2c282409a464d89707312d..5346b7856916167d9ebef4744f9b46132e33304c 100644
--- a/tools/qemu-diff/src/diff-test.c
+++ b/tools/qemu-diff/src/diff-test.c
@@ -3,7 +3,7 @@
 #include <signal.h>
 #include "isa.h"
 
-bool gdb_connect_qemu(void);
+bool gdb_connect_qemu(int);
 bool gdb_memcpy_to_qemu(uint32_t, void *, int);
 bool gdb_getregs(union isa_gdb_regs *);
 bool gdb_setregs(union isa_gdb_regs *);
@@ -34,7 +34,10 @@ void difftest_exec(uint64_t n) {
   while (n --) gdb_si();
 }
 
-void difftest_init(void) {
+void difftest_init(int port) {
+  char buf[32];
+  sprintf(buf, "tcp::%d", port);
+
   int ppid_before_fork = getpid();
   int pid = fork();
   if (pid == -1) {
@@ -57,15 +60,15 @@ void difftest_init(void) {
     }
 
     close(STDIN_FILENO);
-    execlp(ISA_QEMU_BIN, ISA_QEMU_BIN, ISA_QEMU_ARGS "-S", "-s", "-nographic", NULL);
+    execlp(ISA_QEMU_BIN, ISA_QEMU_BIN, ISA_QEMU_ARGS "-S", "-gdb", buf, "-nographic", NULL);
     perror("exec");
     assert(0);
   }
   else {
     // father
 
-    gdb_connect_qemu();
-    printf("Connect to QEMU successfully\n");
+    gdb_connect_qemu(port);
+    printf("Connect to QEMU with %s tcpsuccessfully\n", buf);
 
     atexit(gdb_exit);
 
diff --git a/tools/qemu-diff/src/gdb-host.c b/tools/qemu-diff/src/gdb-host.c
index 341ab851ec5455c3b75fee1f1984f5e74b82f5a9..056176206a8931d31587b10a4a3f6aa924432d03 100644
--- a/tools/qemu-diff/src/gdb-host.c
+++ b/tools/qemu-diff/src/gdb-host.c
@@ -2,9 +2,9 @@
 
 static struct gdb_conn *conn;
 
-bool gdb_connect_qemu(void) {
+bool gdb_connect_qemu(int port) {
   // connect to gdbserver on localhost port 1234
-  while ((conn = gdb_begin_inet("127.0.0.1", 1234)) == NULL) {
+  while ((conn = gdb_begin_inet("127.0.0.1", port)) == NULL) {
     usleep(1);
   }