LibCore: Fix UDPServer up to properly receive data

Prior to this, UDPServer was using listen/accept, which does not make
sense in the context of UDP.

Libraries/LibCore/UDPServer.cpp

@@ -30,7 +30,6 @@
 #include <LibCore/UDPServer.h>
 #include <LibCore/UDPSocket.h>
 #include <stdio.h>
-#include <sys/socket.h>
 
 namespace Core {
 
@@ -45,41 +44,36 @@ UDPServer::~UDPServer()
 {
 }
 
-bool UDPServer::listen(const IPv4Address& address, u16 port)
+bool UDPServer::bind(const IPv4Address& address, u16 port)
 {
-    if (m_listening)
+    if (m_bound)
         return false;
 
     int rc;
-    auto socket_address = SocketAddress(address, port);
-    auto in = socket_address.to_sockaddr_in();
+    auto saddr = SocketAddress(address, port);
+    auto in = saddr.to_sockaddr_in();
+
     rc = ::bind(m_fd, (const sockaddr*)&in, sizeof(in));
     ASSERT(rc == 0);
 
-    rc = ::listen(m_fd, 5);
-    ASSERT(rc == 0);
-    m_listening = true;
-
     m_notifier = Notifier::construct(m_fd, Notifier::Event::Read, this);
     m_notifier->on_ready_to_read = [this] {
-        if (on_ready_to_accept)
-            on_ready_to_accept();
+        if (on_ready_to_receive)
+            on_ready_to_receive();
     };
     return true;
 }
 
-RefPtr<UDPSocket> UDPServer::accept()
+ByteBuffer UDPServer::receive(size_t size, sockaddr_in& in)
 {
-    ASSERT(m_listening);
-    sockaddr_in in;
-    socklen_t in_size = sizeof(in);
-    int accepted_fd = ::accept(m_fd, (sockaddr*)&in, &in_size);
-    if (accepted_fd < 0) {
-        perror("accept");
-        return nullptr;
+    auto buf = ByteBuffer::create_zeroed(size);
+    socklen_t in_len = sizeof(in);
+    ssize_t rlen = ::recvfrom(m_fd, buf.data(), size, 0, (sockaddr*)&in, &in_len);
+    if (rlen < 0) {
+        dbg() << "recvfrom: " << strerror(errno);
+        return {};
     }
-
-    return UDPSocket::construct(accepted_fd);
+    return buf;
 }
 
 Optional<IPv4Address> UDPServer::local_address() const

Libraries/LibCore/UDPServer.h

@@ -26,10 +26,12 @@
 
 #pragma once
 
+#include <AK/ByteBuffer.h>
 #include <AK/Forward.h>
 #include <AK/Function.h>
 #include <LibCore/Forward.h>
 #include <LibCore/Object.h>
+#include <LibCore/SocketAddress.h>
 
 namespace Core {
 
@@ -38,21 +40,26 @@ class UDPServer : public Object {
 public:
     virtual ~UDPServer() override;
 
-    bool is_listening() const { return m_listening; }
-    bool listen(const IPv4Address& address, u16 port);
+    bool is_bound() const { return m_bound; }
 
-    RefPtr<UDPSocket> accept();
+    bool bind(const IPv4Address& address, u16 port);
+    ByteBuffer receive(size_t size, sockaddr_in& from);
+    ByteBuffer receive(size_t size)
+    {
+        struct sockaddr_in saddr;
+        return receive(size, saddr);
+    };
 
     Optional<IPv4Address> local_address() const;
     Optional<u16> local_port() const;
 
-    Function<void()> on_ready_to_accept;
+    Function<void()> on_ready_to_receive;
 
 private:
     explicit UDPServer(Object* parent = nullptr);
 
     int m_fd { -1 };
-    bool m_listening { false };
+    bool m_bound { false };
     RefPtr<Notifier> m_notifier;
 };