diff --git a/src/client.py b/src/client.py
index e69de29..6138ede 100644
--- a/src/client.py
+++ b/src/client.py
@@ -0,0 +1,185 @@
+from fastapi import FastAPI, HTTPException
+import requests
+import os
+from typing import Tuple
+from tpre import *
+import sqlite3
+from contextlib import asynccontextmanager
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    init()
+    yield
+    clean_env()
+
+
+app = FastAPI(lifespan=lifespan)
+
+pk = point
+sk = int
+
+
+def init():
+    global pk, sk
+    init_db()
+    pk, sk = GenerateKeyPair()
+    get_node_list(6)
+
+
+def init_db():
+    with sqlite3.connect("client.db") as db:
+        # message table
+        db.execute(
+            """
+            CREATE TABLE IF NOT EXISTS message (
+                id INTEGER PRIMARY KEY,
+                capsule TEXT,
+                ct TEXT,
+                senderip TEXT
+            );
+        """
+        )
+
+        # node ip table
+        db.execute(
+            """
+            CREATE TABLE IF NOT EXISTS node (
+                id INTEGER PRIMARY KEY,
+                nodeip TEXT
+            );
+        """
+        )
+
+        # sender info table
+        db.execute(
+            """
+            CREATE TABLE IF NOT EXISTS senderinfo (
+                id INTEGER PRIMARY KEY,
+                ip TEXT,
+                publickey TEXT,
+                threshold INTEGER
+            )
+            """
+        )
+        db.commit()
+        print("Init Database Successful")
+
+
+# execute on exit
+def clean_env():
+    print("Exit app")
+
+
+# main page
+@app.get("/")
+async def read_root():
+    return {"message": "Hello, World!"}
+
+
+# receive messages from node
+@app.post("/receive_messages")
+async def receive_messages(C: Tuple[capsule, int], ip: str):
+    """
+    receive capsule and ip from nodes
+    params:
+    C: capsule and ct
+    ip: sender ip
+    return:
+
+    """
+    if not C or not ip:
+        raise HTTPException(status_code=400, detail="Invalid input data")
+
+    capsule, ct = C
+    if not Checkcapsule(capsule):
+        raise HTTPException(status_code=400, detail="Invalid capsule")
+
+    # insert record into database
+    with sqlite3.connect("message.db") as db:
+        try:
+            db.execute(
+                "INSERT INTO message (capsule_column, ct_column, ip_column) VALUES (?, ?, ?)",
+                (capsule, ct, ip),
+            )
+            db.commit()
+            await check_merge(db, ct, ip)
+            return HTTPException(status_code=200, detail="Message received")
+        except Exception as e:
+            print(f"Error occurred: {e}")
+            db.rollback()
+            return HTTPException(status_code=400, detail="Database error")
+
+
+# check record count
+async def check_merge(db, ct: int, ip: str):
+    global sk, pk
+    # Check if the combination of ct_column and ip_column appears more than once.
+    cursor = db.execute(
+        """
+    SELECT capsule, ct 
+    FROM message  
+    WHERE ct = ? AND senderip = ?
+    """,
+        (ct, ip),
+    )
+    # [(capsule, ct), ...]
+    cfrag_cts = cursor.fetchall()
+
+    # get N
+    cursor = db.execute(
+        """
+    SELECT publickey, threshold 
+    FROM senderinfo
+    WHERE senderip = ?
+    """,
+        (ip),
+    )
+    result = cursor.fetchall()
+    pk_sender, T = result[0]
+    if len(cfrag_cts) >= T:
+        cfrags = mergecfrag(cfrag_cts)
+        m = DecryptFrags(sk, pk, pk_sender, cfrags)  # type: ignore
+
+
+# send message to node
+@app.post("/send_message")
+async def send_message(ip: tuple[str, ...]):
+    return 0
+
+
+# request message from others
+@app.post("/request_message")
+async def request_message(ip):
+    return 0
+
+# get node list from central server
+def get_node_list(count: int):
+    server_addr = ""
+    url = "http://" + server_addr + "/server/send_nodes_list"
+    payload = {"count": count}
+    response = requests.post(url, json=payload)
+    # Checking the response
+    if response.status_code == 200:
+        print("Success get node list")
+        node_ip = response.text
+        # insert node ip to database
+        with sqlite3.connect("client.db") as db:
+            db.executemany(
+                """
+                INSERT INTO node 
+                nodeip 
+                VALUE (?)
+                """,
+                node_ip,
+            )
+            db.commit()
+        print("Success add node ip")
+    else:
+        print("Failed:", response.status_code, response.text)
+
+
+if __name__ == "__main__":
+    import uvicorn  # pylint: disable=e0401
+
+    uvicorn.run("client:app", host="0.0.0.0", port=8000)