diff --git a/cmd/client/main.go b/cmd/client/main.go
index 5673cb2..38cce29 100644
--- a/cmd/client/main.go
+++ b/cmd/client/main.go
@@ -1,15 +1,23 @@
 package main
 
 import (
+	"context"
 	"crypto/tls"
 	"crypto/x509"
 	"fmt"
+	"io"
 	"log"
+	"net"
 	"os"
+	"sync"
+	"time"
 
+	"git.qowevisa.me/Qowevisa/gotell/communication"
 	"git.qowevisa.me/Qowevisa/gotell/env"
 )
 
+var messageChannel chan ([]byte)
+
 func main() {
 	host, err := env.GetHost()
 	if err != nil {
@@ -42,22 +50,49 @@ func main() {
 	defer conn.Close()
 
 	log.Println("client: connected to: ", conn.RemoteAddr())
+	ctx, cancel := context.WithCancel(context.Background())
+	wg := &sync.WaitGroup{}
+	wg.Add(1)
+	go func(ctx context.Context, wg *sync.WaitGroup) {
+		defer wg.Done() // Mark this goroutine as done when it exits
+		buf := make([]byte, 1024)
+		for {
+			select {
+			case <-ctx.Done(): // Check if context cancellation has been requested
+				return
+			default:
+				timeoutDuration := 5 * time.Second
+				err := conn.SetReadDeadline(time.Now().Add(timeoutDuration))
+				if err != nil {
+					panic(err)
+				}
+				n, err := conn.Read(buf)
+				if err != nil {
+					if err != io.EOF {
+						if netErr, ok := err.(net.Error); ok && netErr.Timeout() {
+							continue
+						}
+						panic(err)
+					}
+					return
+				}
+				messageChannel <- buf[:n]
+			}
+		}
+	}(ctx, wg)
+	go func() {
+		for message := range messageChannel {
+			msg, err := communication.Decode(message)
+			if err != nil {
+				log.Printf("ERROR: %v\n", err)
+			}
+			switch msg.From {
+			case communication.FROM_SERVER:
 
-	message := "Hello secure Server\n"
-	n, err := conn.Write([]byte(message))
-	if err != nil {
-		log.Fatalf("client: write: %s", err)
-	}
-
-	log.Printf("client: wrote %q (%d bytes)", message, n)
-
-	reply := make([]byte, 256)
-	n, err = conn.Read(reply)
-	if err != nil {
-		log.Fatalf("client: read: %s", err)
-	}
-
-	log.Printf("client: read %q (%d bytes)", string(reply[:n]), n)
-
-	log.Print("client: exiting")
+			case communication.FROM_CLIENT:
+			}
+		}
+	}()
+	cancel()
+	wg.Wait()
 }
diff --git a/cmd/server/main.go b/cmd/server/main.go
index 9c00f07..b0e4c27 100644
--- a/cmd/server/main.go
+++ b/cmd/server/main.go
@@ -3,16 +3,18 @@ package main
 import (
 	"crypto/rand"
 	"crypto/tls"
+	"encoding/binary"
 	"fmt"
 	"io"
 	"log"
 	"net"
 
-	"git.qowevisa.me/Qowevisa/gotell/communication"
+	com "git.qowevisa.me/Qowevisa/gotell/communication"
 	"git.qowevisa.me/Qowevisa/gotell/env"
 )
 
 func main() {
+	userCenter.Init()
 	host, err := env.GetHost()
 	if err != nil {
 		log.Fatal(err)
@@ -53,7 +55,7 @@ func main() {
 func handleClient(conn net.Conn) {
 	defer conn.Close()
 	buf := make([]byte, 512)
-	ask, err := communication.AskClientNickname()
+	ask, err := com.ServerAskClientAboutNickname()
 	if err != nil {
 		log.Printf("ERROR: %#v\n", err)
 	} else {
@@ -72,18 +74,41 @@ func handleClient(conn net.Conn) {
 			}
 			break
 		}
-		answer := append([]byte("Hello! I see your message:"), buf[:n]...)
-		msg, err := communication.JustGetMessage(answer)
+		msg, err := com.Decode(buf[:n])
 		if err != nil {
 			log.Printf("ERROR: %#v\n", err)
 			continue
 		}
-		log.Printf("server: conn: sending %#v\n", msg)
-		_, err = conn.Write(msg)
-		if err != nil {
-			log.Printf("server: conn: write: %s", err)
-			break
+		if msg == nil {
+			log.Printf("ERROR MSG IS NIL\n")
+			continue
 		}
+		log.Printf("server: conn: receive %#v\n", *msg)
+		// Handle
+		switch msg.ID {
+		case com.ID_CLIENT_SEND_SERVER_NICKNAME:
+			id, err := userCenter.AddUser(string(msg.Data))
+			if err != nil {
+				answ, err := com.ServerSendClientDecline()
+				if err != nil {
+					log.Printf("ERROR: %v\n", err)
+					continue
+				}
+				conn.Write(answ)
+			} else {
+				idBytes := make([]byte, 4)
+				binary.BigEndian.PutUint32(idBytes, uint32(id))
+				answ, err := com.ServerSendClientHisID(idBytes)
+				if err != nil {
+					log.Printf("ERROR: %v\n", err)
+					continue
+				}
+				conn.Write(answ)
+			}
+		case com.ID_CLIENT_SEND_SERVER_LINK:
+		default:
+		}
+		// Handle
 	}
 	log.Println("server: conn: closed")
 }
diff --git a/cmd/server/users.go b/cmd/server/users.go
new file mode 100644
index 0000000..a5c7e6a
--- /dev/null
+++ b/cmd/server/users.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"errors"
+	"math/rand"
+	"sync"
+)
+
+var (
+	userCenter UserCenter
+)
+
+type UserCenter struct {
+	UsersSTOI map[string]int32
+	UsersITOS map[int32]string
+	Mu        sync.Mutex
+}
+
+func (u *UserCenter) Init() {
+	u.UsersSTOI = make(map[string]int32)
+	u.UsersITOS = make(map[int32]string)
+}
+
+var (
+	ERROR_ALREADY_HAVE = errors.New("Username is already taken")
+	ERROR_DONT_HAVE    = errors.New("Username was not found")
+)
+
+func (u *UserCenter) AddUser(name string) (int32, error) {
+	u.Mu.Lock()
+	defer u.Mu.Unlock()
+	_, alreadyHave := u.UsersSTOI[name]
+	if alreadyHave {
+		return -1, ERROR_ALREADY_HAVE
+	}
+	var ret int32
+	for {
+		rInt := rand.Int31()
+		_, taken := u.UsersITOS[rInt]
+		if !taken {
+			ret = rInt
+			break
+		}
+	}
+	u.UsersITOS[ret] = name
+	u.UsersSTOI[name] = ret
+	return ret, nil
+}
+
+func (u *UserCenter) GetID(name string) (int32, error) {
+	id, have := u.UsersSTOI[name]
+	if !have {
+		return -1, ERROR_DONT_HAVE
+	}
+	return id, nil
+}
+
+func (u *UserCenter) GetName(id int32) (string, error) {
+	name, have := u.UsersITOS[id]
+	if !have {
+		return "", ERROR_DONT_HAVE
+	}
+	return name, nil
+}