espat: add support for esp8266/esp32 Wifi adaptor AT command set with net-compatible UDP support

Signed-off-by: Ron Evans <ron@hybridgroup.com>

espat/net.go

@@ -0,0 +1,143 @@
+package espat
+
+import (
+	"strconv"
+	"time"
+)
+
+// DialUDP makes a UDP network connection. raadr is the port that the messages will
+// be sent to, and laddr is the port that will be listened to in order to
+// receive incoming messages.
+func (d Device) DialUDP(network string, laddr, raddr *UDPAddr) (*SerialConn, error) {
+	addr := raddr.IP.String()
+	sendport := strconv.Itoa(raddr.Port)
+	listenport := strconv.Itoa(laddr.Port)
+
+	// disconnect any old socket
+	d.DisconnectSocket()
+
+	// connect new socket
+	d.ConnectUDPSocket(addr, sendport, listenport)
+
+	return &SerialConn{Adaptor: &d, laddr: laddr, raddr: raddr}, nil
+}
+
+// ListenUDP listens for UDP connections on the port listed in laddr.
+func (d Device) ListenUDP(network string, laddr *UDPAddr) (*SerialConn, error) {
+	addr := "0"
+	sendport := "0"
+	listenport := strconv.Itoa(laddr.Port)
+
+	// disconnect any old socket
+	d.DisconnectSocket()
+
+	// connect new socket
+	d.ConnectUDPSocket(addr, sendport, listenport)
+
+	return &SerialConn{Adaptor: &d, laddr: laddr}, nil
+}
+
+// SerialConn is a loosely net.Conn compatible intended to support
+// TCP/UDP over serial.
+type SerialConn struct {
+	Adaptor *Device
+	laddr   *UDPAddr
+	raddr   *UDPAddr
+}
+
+// Read reads data from the connection.
+// TODO: implement the full method functionality:
+// Read can be made to time out and return an Error with Timeout() == true
+// after a fixed time limit; see SetDeadline and SetReadDeadline.
+func (c *SerialConn) Read(b []byte) (n int, err error) {
+	// read only the data that has been received via "+IPD" socket
+	return c.Adaptor.ReadSocket(b)
+}
+
+// Write writes data to the connection.
+// TODO: implement the full method functionality for timeouts.
+// Write can be made to time out and return an Error with Timeout() == true
+// after a fixed time limit; see SetDeadline and SetWriteDeadline.
+func (c *SerialConn) Write(b []byte) (n int, err error) {
+	// specify that is a data transfer to the
+	// currently open socket, not commands to the ESP8266/ESP32.
+	c.Adaptor.StartSocketSend(len(b))
+	return c.Adaptor.Write(b)
+}
+
+// Close closes the connection.
+// Currently only supports a single Read or Write operations without blocking.
+func (c *SerialConn) Close() error {
+	c.Adaptor.DisconnectSocket()
+	return nil
+}
+
+// LocalAddr returns the local network address.
+func (c *SerialConn) LocalAddr() UDPAddr {
+	return *c.laddr
+}
+
+// RemoteAddr returns the remote network address.
+func (c *SerialConn) RemoteAddr() UDPAddr {
+	return *c.laddr
+}
+
+// SetDeadline sets the read and write deadlines associated
+// with the connection. It is equivalent to calling both
+// SetReadDeadline and SetWriteDeadline.
+//
+// A deadline is an absolute time after which I/O operations
+// fail with a timeout (see type Error) instead of
+// blocking. The deadline applies to all future and pending
+// I/O, not just the immediately following call to Read or
+// Write. After a deadline has been exceeded, the connection
+// can be refreshed by setting a deadline in the future.
+//
+// An idle timeout can be implemented by repeatedly extending
+// the deadline after successful Read or Write calls.
+//
+// A zero value for t means I/O operations will not time out.
+func (c *SerialConn) SetDeadline(t time.Time) error {
+	return nil
+}
+
+// SetReadDeadline sets the deadline for future Read calls
+// and any currently-blocked Read call.
+// A zero value for t means Read will not time out.
+func (c *SerialConn) SetReadDeadline(t time.Time) error {
+	return nil
+}
+
+// SetWriteDeadline sets the deadline for future Write calls
+// and any currently-blocked Write call.
+// Even if write times out, it may return n > 0, indicating that
+// some of the data was successfully written.
+// A zero value for t means Write will not time out.
+func (c *SerialConn) SetWriteDeadline(t time.Time) error {
+	return nil
+}
+
+// The following definitions are here to support a Golang standard package
+// net-compatible interface for IP until TinyGo can compile the net package.
+
+// IP is an IP address. Unlike the standard implementation, it is only
+// a buffer of bytes that contains the string form of the IP address, not the
+// full byte format used by the Go standard .
+type IP []byte
+
+// UDPAddr here to serve as compatible type. until TinyGo can compile the net package.
+type UDPAddr struct {
+	IP   IP
+	Port int
+	Zone string // IPv6 scoped addressing zone; added in Go 1.1
+}
+
+// ParseIP parses s as an IP address, returning the result.
+func ParseIP(s string) IP {
+	return IP([]byte(s))
+}
+
+// String returns the string form of the IP address ip.
+func (ip IP) String() string {
+	return string(ip)
+}