diff --git a/simpleChatting/comn.h b/simpleChatting/comn.h
new file mode 100644
index 0000000000000000000000000000000000000000..de89e9765b29c4b6526ae034b20fdad4e70e741f
--- /dev/null
+++ b/simpleChatting/comn.h
@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <sys/ipc.h>
+#include <sys/shm.h>
+
+#define MAX_USER_CNT 2
+#define MAX_USER_NAME 10
+#define MAX_CHAT_LENGTH 255
+
+int isServerConn = -1;
+int shmid = 0;
+void *shmaddr = NULL;
+struct shmid_ds info;
+
+typedef struct UserData
+{
+    int pid;
+    char name[MAX_USER_NAME];
+}UserData;
+
+typedef struct SharedData
+{
+    int pid;
+    UserData user[MAX_USER_CNT];
+}SharedData;
+
+typedef struct MessageData
+{
+    int send_pid;
+    char content[MAX_CHAT_LENGTH];
+}MsgData;