Accept server sockets with non-blocking enabled

net/src/main/scala/epollcat/internal/net/EpollAsyncServerSocketChannel.scala

@@ -125,7 +125,7 @@ final class EpollAsyncServerSocketChannel private (fd: Int)
       handler: CompletionHandler[AsynchronousSocketChannel, _ >: A]
   ): Unit = {
     if (readReady) {
-      val clientFd = syssocket.accept(fd, null, null)
+      val clientFd = syssocket.accept4(fd, null, null, EpollAsyncSocketChannel.SOCK_NONBLOCK)
       if (clientFd == -1) {
         if (errno.errno == posix.errno.EAGAIN || errno.errno == posix.errno.EWOULDBLOCK) {
           readReady = false
@@ -183,5 +183,5 @@ object EpollAsyncServerSocketChannel {
 @extern
 @nowarn
 private[net] object syssocket {
-  def accept(sockfd: CInt, addr: Ptr[Byte], addrlen: Ptr[Byte]): CInt = extern
+  def accept4(sockfd: CInt, addr: Ptr[Byte], addrlen: Ptr[Byte], flags: CInt): CInt = extern
 }

net/src/main/scala/epollcat/internal/net/EpollAsyncSocketChannel.scala

@@ -351,7 +351,7 @@ final class EpollAsyncSocketChannel private (fd: Int) extends AsynchronousSocket
 }
 
 object EpollAsyncSocketChannel {
-  private final val SOCK_NONBLOCK = 2048
+  final val SOCK_NONBLOCK = 2048
 
   def open(): EpollAsyncSocketChannel = {
     val fd = posix

tests/shared/src/test/scala/epollcat/tcp/TcpSuite.scala

@@ -229,4 +229,23 @@ class TcpSuite extends EpollcatSuite {
       .intercept[ClosedChannelException]
   }
 
+  test("server socket read does not block") {
+    IOServerSocketChannel.open.use { server =>
+      IOSocketChannel.open.use { clientCh =>
+        for {
+          _ <- server.bind(new InetSocketAddress(0))
+          addr <- server.localAddress
+          _ <- clientCh.connect(addr)
+          _ <- clientCh.write(ByteBuffer.wrap("Hello!".getBytes))
+          _ <- server.accept.use { serverCh =>
+            for {
+              bb <- IO(ByteBuffer.allocate(8192))
+              _ <- serverCh.read(bb)
+            } yield ()
+          }
+        } yield ()
+      }
+    }
+  }
+
 }