diff --git a/Kernel/Net/TCPSocket.cpp b/Kernel/Net/TCPSocket.cpp
index e6e3150f3b..076e2d2be1 100644
--- a/Kernel/Net/TCPSocket.cpp
+++ b/Kernel/Net/TCPSocket.cpp
@@ -245,6 +245,7 @@ KResult TCPSocket::send_tcp_packet(u16 flags, const UserOrKernelBuffer* payload,
     if (tcp_packet.has_syn() || payload_size > 0) {
         Locker locker(m_not_acked_lock);
         m_not_acked.append({ m_sequence_number, move(packet), ipv4_payload_offset, *routing_decision.adapter });
+        m_not_acked_size += payload_size;
         enqueue_for_retransmit();
     }
 
@@ -269,6 +270,10 @@ void TCPSocket::receive_tcp_packet(const TCPPacket& packet, u16 size)
                 auto old_adapter = packet.adapter.strong_ref();
                 if (old_adapter)
                     old_adapter->release_packet_buffer(*packet.buffer);
+                TCPPacket& tcp_packet = *(TCPPacket*)(packet.buffer->buffer.data() + packet.ipv4_payload_offset);
+                auto payload_size = packet.buffer->buffer.data() + packet.buffer->buffer.size() - (u8*)tcp_packet.payload();
+                m_not_acked_size -= payload_size;
+                evaluate_block_conditions();
                 m_not_acked.take_first();
                 removed++;
             } else {
@@ -566,4 +571,16 @@ void TCPSocket::retransmit_packets()
     }
 }
 
+bool TCPSocket::can_write(const FileDescription& file_description, size_t size) const
+{
+    if (!IPv4Socket::can_write(file_description, size))
+        return false;
+
+    if (!file_description.is_blocking())
+        return true;
+
+    Locker lock(m_not_acked_lock);
+    return m_not_acked_size + size <= m_send_window_size;
+}
+
 }
diff --git a/Kernel/Net/TCPSocket.h b/Kernel/Net/TCPSocket.h
index 7dab47d57f..c3ac398301 100644
--- a/Kernel/Net/TCPSocket.h
+++ b/Kernel/Net/TCPSocket.h
@@ -157,6 +157,8 @@ public:
 
     virtual KResult close() override;
 
+    virtual bool can_write(const FileDescription&, size_t) const override;
+
 protected:
     void set_direction(Direction direction) { m_direction = direction; }
 
@@ -200,8 +202,9 @@ private:
         int tx_counter { 0 };
     };
 
-    Lock m_not_acked_lock { "TCPSocket unacked packets" };
+    mutable Lock m_not_acked_lock { "TCPSocket unacked packets" };
     SinglyLinkedList<OutgoingPacket> m_not_acked;
+    size_t m_not_acked_size { 0 };
 
     u32 m_duplicate_acks { 0 };
 
@@ -212,6 +215,9 @@ private:
     static constexpr u32 maximum_retransmits = 5;
     Time m_last_retransmit_time;
     u32 m_retransmit_attempts { 0 };
+
+    // FIXME: Parse window size TCP option from the peer
+    u32 m_send_window_size { 64 * KiB };
 };
 
 }