diff --git a/sample.go b/sample.go
index 6179684..76f1813 100644
--- a/sample.go
+++ b/sample.go
@@ -2,46 +2,79 @@ package main
 
 import (
     "bufio"
+    "encoding/json"
     "fmt"
     "gopkg.in/zeromq/goczmq.v4"
     "log"
     "os"
+    "os/signal"
     "strings"
     "time"
 )
 
+const (
+    defaultProofHeader = "proofblock"
+    defaultHash        = "0x0000000000000000000"
+)
+
+type Proof struct {
+    Type      string `json:"type"`
+    Timestamp string `json:"timestamp,omitempty"`
+    Data      string `json:"data"`
+}
+
 func main() {
-    ep := "tcp://34.71.52.251:40000"
+    ep := os.Getenv("PROOF_ENDPOINT")
+    if ep == "" {
+        ep = "tcp://34.71.52.251:40000"
+    }
+
     sample := goczmq.NewReqChanneler(ep)
     if sample == nil {
-        log.Fatal("Failed to subscribe to endpoint: ", ep)
+        log.Fatalf("Failed to subscribe to endpoint: %s", ep)
     }
     defer sample.Destroy()
 
-    // Prompt the user for input
+    // Graceful shutdown on Ctrl+C
+    c := make(chan os.Signal, 1)
+    signal.Notify(c, os.Interrupt)
+    go func() {
+        <-c
+        log.Println("Interrupt received, shutting down.")
+        sample.Destroy()
+        os.Exit(0)
+    }()
+
     reader := bufio.NewReader(os.Stdin)
     fmt.Print("Enter proof data (or press Enter to use default): ")
-    input, _ := reader.ReadString('\n')
+    input, err := reader.ReadString('\n')
+    if err != nil {
+        log.Fatalf("Failed to read input: %v", err)
+    }
     input = strings.TrimSpace(input)
 
-    // Let the socket connect
-    time.Sleep(5 * time.Second)
+    time.Sleep(5 * time.Second) // Wait for connection
 
-    // Prepare the proof data
-    var proof [][]byte
+    var proof Proof
     if input == "" {
-        // Use default value if no input is provided
-        proof = [][]byte{[]byte("proofblock"), []byte("timestamp :" + time.Now().String()), []byte("0x0000000000000000000")}
+        proof = Proof{Type: defaultProofHeader, Timestamp: time.Now().String(), Data: defaultHash}
     } else {
-        // Use user-provided input
-        proof = [][]byte{[]byte("proofblock"), []byte(input), []byte("!!!!!")}
+        proof = Proof{Type: defaultProofHeader, Data: input}
     }
 
-    // Send the proof
-    sample.SendChan <- proof
-    fmt.Printf("Proof sent: %s\n", proof)
+    jsonProof, err := json.Marshal(proof)
+    if err != nil {
+        log.Fatalf("Failed to encode proof as JSON: %v", err)
+    }
+
+    select {
+    case sample.SendChan <- [][]byte{jsonProof}:
+        log.Printf("Proof sent: %s", jsonProof)
+    case <-time.After(5 * time.Second):
+        log.Println("Timed out while trying to send proof.")
+        return
+    }
 
-    // Receive the response
     resp := <-sample.RecvChan
-    fmt.Printf("Response received: %s\n", resp)
+    log.Printf("Response received: %s", resp)
 }