diff --git a/kern/src/ec.cc b/kern/src/ec.cc
index 7a5b1fa..899993e 100644
--- a/kern/src/ec.cc
+++ b/kern/src/ec.cc
@@ -284,8 +284,20 @@ void Ec::sys_call()
 
     printf("EC:%p SYS_CALL (PT=%u)\n", current, pt->id);
 
-    // TODO copy message if ready and switch
-    FAIL;
+    Ec *recv = pt->recv;
+
+    if (recv->state == WAITING) {
+        current->cont  = ret_user_sysexit;
+        current->state = BLOCKED;
+        recv->cont     = recv_user;
+        recv->caller   = current;
+        recv->state    = READY;
+        recv->sys_regs()->set_ip(pt->rip);
+        recv->make_current();
+    }
+
+    current->cont = sys_call;
+    schedule();
 }
 
 void Ec::sys_reply()
@@ -295,8 +307,14 @@ void Ec::sys_reply()
 
     printf("EC:%p SYS_REPLY\n", current);
 
-    // TODO copy message and switch back
-    FAIL;
+    Ec *caller      = current->caller;
+
+    current->caller = nullptr;
+    current->state  = WAITING;
+    memcpy(caller->utcb, current->utcb, PAGE_SIZE);
+
+    caller->state = READY;
+    caller->make_current();
 }
 
 void Ec::recv_user()
diff --git a/user/src/user.cc b/user/src/user.cc
index d4f247a..143782a 100644
--- a/user/src/user.cc
+++ b/user/src/user.cc
@@ -65,18 +65,21 @@ void sys_reply()
 [[noreturn]]
 void sender()
 {
-    // TODO perform sys_call() in a loop
-    // TODO use dump to print out values
-    while (1)
-        ;
+    unsigned long *words = UTCB_SENDER;
+    words[0]             = 1;
+    words[1]             = 2;
+    while (1) {
+        sys_call(0);
+        sys_dump(words[0], words[1]);
+    }
 }
 
 [[noreturn]]
 void portal()
 {
-    // TODO handle single request and reply
-    while (1)
-        sys_yield();
+    unsigned long *words  = UTCB_RECEIVER;
+    words[0]             += words[1];
+    sys_reply();
 }
 
 extern "C" [[noreturn]]
@@ -88,7 +91,7 @@ void main_func()
     sys_create_ec(sender, stack + 64 * 1, UTCB_SENDER);
     // receiver thread
     sys_create_ec(0, stack + 64 * 2, UTCB_RECEIVER);
-    // TODO create portal
+    sys_create_pt(0, portal, UTCB_RECEIVER);
 
     while (1)
         sys_yield();