diff --git a/transmit.h b/transmit.h
index d765020..72c88b5 100644
--- a/transmit.h
+++ b/transmit.h
@@ -123,6 +123,10 @@ const char transmit_html[] PROGMEM = R"rawliteral(
             background: linear-gradient(135deg, #f2994a 0%, #f2c94c 100%);
             color: white;
         }
+        .btn-info {
+            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
+            color: white;
+        }
         .btn:hover { transform: translateY(-2px); box-shadow: 0 5px 15px rgba(0,0,0,0.3); }
         
         .message-list {
@@ -357,6 +361,15 @@ const char transmit_html[] PROGMEM = R"rawliteral(
                     </div>
                 </div>
                 
+                <div class="form-group" style="margin-bottom: 15px;">
+                    <label>Send All Once - Waiting Time (ms)</label>
+                    <input type="number" id="send-all-delay" value="10" min="0" max="1000" 
+                           style="max-width: 200px; padding: 10px; border: 2px solid #ddd; border-radius: 5px;">
+                    <small style="color: #666; margin-top: 5px; display: block;">
+                        Delay between messages when using "Send All Once" button
+                    </small>
+                </div>
+                
                 <div class="form-group" style="margin-bottom: 15px;">
                     <label>Data Bytes (Hex)</label>
                     <div class="data-bytes">
@@ -381,6 +394,7 @@ const char transmit_html[] PROGMEM = R"rawliteral(
             <div style="margin-bottom: 15px; display: flex; gap: 10px; flex-wrap: wrap;">
                 <button class="btn btn-success" onclick="startAll()">Start All</button>
                 <button class="btn btn-danger" onclick="stopAll()">Stop All</button>
+                <button class="btn btn-info" onclick="sendAllOnce()">📤 Send All Once</button>
                 <button class="btn btn-danger" onclick="clearAll()">Clear All</button>
             </div>
             
@@ -587,6 +601,11 @@ const char transmit_html[] PROGMEM = R"rawliteral(
         }
         
         function sendCanMessage(id, type, dlc, data) {
+            if (!ws || ws.readyState !== WebSocket.OPEN) {
+                alert('WebSocket not connected!');
+                return;
+            }
+            
             const cmd = {
                 cmd: 'sendCan',
                 id: id,
@@ -594,7 +613,9 @@ const char transmit_html[] PROGMEM = R"rawliteral(
                 dlc: dlc,
                 data: data.join('')
             };
+            
             ws.send(JSON.stringify(cmd));
+            console.log('Sent CAN message: ID=' + id + ', DLC=' + dlc + ', Data=' + data.join(''));
         }
         
         function updateMessageList() {
@@ -664,6 +685,61 @@ const char transmit_html[] PROGMEM = R"rawliteral(
             updateMessageList();
         }
         
+        function sendAllOnce() {
+            if (messages.length === 0) {
+                alert('No messages in the list!');
+                return;
+            }
+            
+            if (!ws || ws.readyState !== WebSocket.OPEN) {
+                alert('WebSocket not connected!');
+                return;
+            }
+            
+            const delayMs = parseInt(document.getElementById('send-all-delay').value) || 10;
+            
+            // 버튼 비활성화 및 시각적 피드백
+            const btn = event.target;
+            const originalText = btn.innerHTML;
+            btn.disabled = true;
+            btn.innerHTML = '⏳ Sending...';
+            
+            let sentCount = 0;
+            
+            // 순차적으로 메시지 전송 (딜레이 포함)
+            function sendNext(index) {
+                if (index >= messages.length) {
+                    // 모든 메시지 전송 완료
+                    console.log('Sent all messages once: ' + sentCount + ' messages');
+                    
+                    btn.innerHTML = '✓ Sent ' + sentCount + ' msgs';
+                    btn.style.background = 'linear-gradient(135deg, #11998e 0%, #38ef7d 100%)';
+                    
+                    setTimeout(() => {
+                        btn.innerHTML = originalText;
+                        btn.style.background = '';
+                        btn.disabled = false;
+                    }, 2000);
+                    return;
+                }
+                
+                const msg = messages[index];
+                sendCanMessage(msg.id, msg.type, msg.dlc, msg.data);
+                sentCount++;
+                
+                // 진행 상황 표시
+                btn.innerHTML = '⏳ Sending ' + (index + 1) + '/' + messages.length;
+                
+                // 다음 메시지 전송 (딜레이 후)
+                setTimeout(() => {
+                    sendNext(index + 1);
+                }, delayMs);
+            }
+            
+            // 첫 번째 메시지부터 시작
+            sendNext(0);
+        }
+        
         function clearAll() {
             if (confirm('Clear all messages?')) {
                 stopAll();