diff --git a/piv/internal/pcsc/pcsc.go b/piv/internal/pcsc/pcsc.go
index bed8a20..1bf1967 100644
--- a/piv/internal/pcsc/pcsc.go
+++ b/piv/internal/pcsc/pcsc.go
@@ -12,18 +12,33 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package pcsc implements the libpcsclite protocol for communicating with pcscd.
+//
+// This package is a pure Go implementation of libpcsclite, allowing piv-go to
+// communicate directly with pcscd without cgo. This still relies on pcscd to
+// communicate with the OS, and will be less reliable than linking against the
+// shared libraries provided by the pcscd packages.
+//
+// This package will NOT work with the native Mac and Windows libraries, which
+// are provided directly by the OS. Though pcsclite can be installed on Mac.
 package pcsc
 
 import (
 	"bytes"
 	"context"
 	"encoding/binary"
+	"encoding/hex"
 	"fmt"
 	"io"
 	"net"
 	"os"
 )
 
+// pcscd messages directly encode C structs over a unix domain socket. Determine
+// the host's byte order with build tags so encoding/binary can replicate this
+// behavior.
+//
+// https://groups.google.com/g/golang-nuts/c/3GEzwKfRRQw/m/ppkJKrT4cfAJ
 var nativeByteOrder binary.ByteOrder
 
 const (
@@ -32,40 +47,82 @@ const (
 )
 
 const (
-	scardSSuccess = 0
+	// RVSuccess is a return value indicating the operation succeeded.
+	RVSuccess = 0
+
+	majorVersion = 4
+	minorVersion = 4
 
 	// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L76
-	commandVersion         = 0x11
-	commandGetReadersState = 0x12
+	commandEstablishContext = 0x01
+	commandReleaseContext   = 0x02
+	commandConnect          = 0x04
+	commandDisconnect       = 0x05
+	commandBeginTransaction = 0x07
+	commandEndTransaction   = 0x08
+	commandTransmit         = 0x09
+	commandVersion          = 0x11
+	commandGetReadersState  = 0x12
+
+	// Context modes to be passed to NewContext.
+	//
+	// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/PCSC/pcsclite.h.in#L248
+	Exclusive = 0x0001
+	Shared    = 0x0002
+	Direct    = 0x0003
+
+	// Different protocols that can be used when connecting to a card.
+	ProtocolT0  = 0x0001
+	ProtocolT1  = 0x0002
+	ProtocolRaw = 0x0004
+	ProtocolT15 = 0x0005
+
+	// Disconnect option.
+	LeaveCard   = 0x0000
+	ResetCard   = 0x0001
+	UnpowerCard = 0x0002
+	EjectCard   = 0x0003
 )
 
+// RVError wraps an underlying PCSC error code.
+type RVError struct {
+	RV uint32
+}
+
+// Error returns a string encoding of the error code. Note that human readable
+// messages are not provided by this package, and are handled by the piv
+// package instead.
+func (r *RVError) Error() string {
+	return fmt.Sprintf("rv 0x%x", r.RV)
+}
+
+// Client represents a connection with the pcscd process.
 type Client struct {
 	conn net.Conn
 }
 
+// Close releases the underlying connection. It does not release any contexts
+// which must be closed separately.
 func (c *Client) Close() error {
 	return c.conn.Close()
 }
 
-func (c *Client) version() (major, minor int32, err error) {
+func (c *Client) checkVersion() error {
 	req := struct {
 		Major int32
 		Minor int32
 		RV    uint32
-	}{4, 4, scardSSuccess}
-
-	var resp struct {
-		Major int32
-		Minor int32
-		RV    uint32
+	}{majorVersion, minorVersion, RVSuccess}
+	if err := c.sendMessage(commandVersion, req, &req); err != nil {
+		return fmt.Errorf("send message: %v", err)
 	}
-	if err := c.sendMessage(commandVersion, req, &resp); err != nil {
-		return 0, 0, fmt.Errorf("send message: %v", err)
+	if req.RV != RVSuccess {
+		return &RVError{RV: req.RV}
 	}
-	if resp.RV != scardSSuccess {
-		return 0, 0, fmt.Errorf("invalid response value: %x", resp.RV)
+	if req.Major != majorVersion {
+		return fmt.Errorf("unsupported major version of pcscd protocol: %d", req.Major)
 	}
-	return resp.Major, resp.Minor, nil
+	return nil
 }
 
 const (
@@ -77,25 +134,14 @@ const (
 	maxReaders = 16
 )
 
-// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/eventhandler.h#L52
-// 	typedef struct pubReaderStatesList
-// 	{
-// 		char readerName[MAX_READERNAME]; /**< reader name */
-// 		uint32_t eventCounter; /**< number of card events */
-// 		uint32_t readerState; /**< SCARD_* bit field */
-// 		int32_t readerSharing; /**< PCSCLITE_SHARING_* sharing status */
+// readerState holds metadata about a PCSC card.
 //
-// 		UCHAR cardAtr[MAX_ATR_SIZE]; /**< ATR */
-// 		uint32_t cardAtrLength; /**< ATR length */
-// 		uint32_t cardProtocol; /**< SCARD_PROTOCOL_* value */
-// 	}
-// 	READER_STATE;
-
+// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/eventhandler.h#L52
 type readerState struct {
 	Name         [maxReaderNameSize]byte
 	EventCounter uint32
 	State        uint32
-	Sharing      uint32
+	Sharing      int32
 
 	Attr     [maxAttributeSize]byte
 	AttrSize uint32
@@ -115,11 +161,11 @@ func (r readerState) name() string {
 	return string(r.Name[:i])
 }
 
-func (c *Client) readers() ([]string, error) {
-	var resp [maxReaders]readerState
-
-	if err := c.sendMessage(commandGetReadersState, nil, &resp); err != nil {
-		return nil, fmt.Errorf("send message: %v", err)
+// Readers returns the names of all readers that are connected to the device.
+func (c *Client) Readers() ([]string, error) {
+	resp, err := c.readers()
+	if err != nil {
+		return nil, err
 	}
 
 	var names []string
@@ -132,6 +178,182 @@ func (c *Client) readers() ([]string, error) {
 	return names, nil
 }
 
+func (c *Client) readers() (states [maxReaders]readerState, err error) {
+	if err := c.sendMessage(commandGetReadersState, nil, &states); err != nil {
+		return states, fmt.Errorf("send message: %v", err)
+	}
+	return states, nil
+}
+
+// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L118
+type establishRequest struct {
+	Scope   uint32
+	Context uint32
+	RV      uint32
+}
+
+// Context holds an open PCSC context, which is required to perform actions
+// such as starting transactions or transmitting data to a card.
+type Context struct {
+	client  *Client
+	context uint32
+}
+
+// NewContext attempts to establish a context with the PCSC daemon. The returned
+// context is only valid while the client is open.
+func (c *Client) NewContext() (*Context, error) {
+	const scopeSystem = 0x0002
+	req := establishRequest{
+		Scope: scopeSystem,
+		RV:    RVSuccess,
+	}
+	if err := c.sendMessage(commandEstablishContext, req, &req); err != nil {
+		return nil, fmt.Errorf("establish context: %v", err)
+	}
+	if req.RV != RVSuccess {
+		return nil, &RVError{RV: req.RV}
+	}
+	return &Context{client: c, context: req.Context}, nil
+}
+
+// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L118
+type releaseRequest struct {
+	Context uint32
+	RV      uint32
+}
+
+// Close releases the context with the PCSC daemon.
+func (c *Context) Close() error {
+	req := releaseRequest{
+		Context: c.context,
+		RV:      RVSuccess,
+	}
+	if err := c.client.sendMessage(commandReleaseContext, req, &req); err != nil {
+		return fmt.Errorf("release context: %v", err)
+	}
+	if req.RV != RVSuccess {
+		return &RVError{RV: req.RV}
+	}
+	return nil
+}
+
+// Connection represents a connection to a specific smartcard.
+type Connection struct {
+	client  *Client
+	context uint32
+	card    int32
+}
+
+// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L141
+type connectRequest struct {
+	Context            uint32
+	Reader             [maxReaderNameSize]byte
+	ShareMode          uint32
+	PreferredProtocols uint32
+	Card               int32
+	ActiveProtocols    uint32
+	RV                 uint32
+}
+
+func (c *Context) Connect(reader string, mode uint32) (*Connection, error) {
+	req := connectRequest{
+		Context:            c.context,
+		ShareMode:          Shared,
+		PreferredProtocols: ProtocolT1,
+		RV:                 RVSuccess,
+	}
+
+	if len(reader)+1 > maxReaderNameSize {
+		return nil, fmt.Errorf("reader name too long")
+	}
+	copy(req.Reader[:], []byte(reader))
+
+	if err := c.client.sendMessage(commandConnect, req, &req); err != nil {
+		return nil, fmt.Errorf("send message: %v", err)
+	}
+	if req.RV != RVSuccess {
+		return nil, &RVError{RV: req.RV}
+	}
+	if req.Card == 0 {
+		return nil, fmt.Errorf("card returned no value")
+	}
+	return &Connection{
+		client: c.client, context: c.context, card: req.Card,
+	}, nil
+}
+
+//https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L172
+type disconnectRequest struct {
+	Card        int32
+	Disposition uint32
+	RV          uint32
+}
+
+func (c *Connection) Close() error {
+	req := disconnectRequest{
+		Card:        c.card,
+		Disposition: LeaveCard,
+		RV:          RVSuccess,
+	}
+
+	if err := c.client.sendMessage(commandDisconnect, req, &req); err != nil {
+		return fmt.Errorf("send message: %v", err)
+	}
+	if req.RV != RVSuccess {
+		return &RVError{RV: req.RV}
+	}
+	return nil
+}
+
+// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L184
+type beginRequest struct {
+	Card int32
+	RV   uint32
+}
+
+// BeginTransaction is called before transmitting data to the card.
+func (c *Connection) BeginTransaction() error {
+	req := beginRequest{
+		Card: c.card,
+		RV:   RVSuccess,
+	}
+
+	if err := c.client.sendMessage(commandBeginTransaction, req, &req); err != nil {
+		return fmt.Errorf("send message: %v", err)
+	}
+	if req.RV != RVSuccess {
+		return &RVError{RV: req.RV}
+	}
+	return nil
+}
+
+// https://github.com/LudovicRousseau/PCSC/blob/1.9.0/src/winscard_msg.h#L195
+type endRequest struct {
+	Card        int32
+	Disposition uint32
+	RV          uint32
+}
+
+func (c *Connection) EndTransaction() error {
+	req := endRequest{
+		Card:        c.card,
+		Disposition: LeaveCard,
+		RV:          RVSuccess,
+	}
+
+	if err := c.client.sendMessage(commandEndTransaction, req, &req); err != nil {
+		return fmt.Errorf("send message: %v", err)
+	}
+	if req.RV != RVSuccess {
+		return &RVError{RV: req.RV}
+	}
+	return nil
+}
+
+func (c *Connection) Transmit(b []byte) ([]byte, error) {
+	return nil, nil
+}
+
 func (c *Client) sendMessage(command uint32, req, resp interface{}) error {
 	var data []byte
 	if req != nil {
@@ -156,16 +378,33 @@ func (c *Client) sendMessage(command uint32, req, resp interface{}) error {
 		return fmt.Errorf("write request bytes: %v", err)
 	}
 
-	if err := binary.Read(c.conn, nativeByteOrder, resp); err != nil {
+	respData := &bytes.Buffer{}
+	if err := binary.Read(io.TeeReader(c.conn, respData), nativeByteOrder, resp); err != nil {
 		return fmt.Errorf("read response: %v", err)
 	}
+
+	fmt.Fprintln(os.Stderr, "Request:")
+	fmt.Fprintln(os.Stderr, hex.Dump(data[8:]))
+
+	fmt.Fprintln(os.Stderr, "Response:")
+	fmt.Fprintln(os.Stderr, hex.Dump(respData.Bytes()))
 	return nil
 }
 
+// Config is used to modify client behavior.
 type Config struct {
+	// SocketPath can be used to override a path to the pcscd socket. This field
+	// is generally not required unless pcscd has been compiled with modified
+	// options.
+	//
+	// This value defaults to the pcsclite behavior, preferring the value of the
+	// PCSCLITE_CSOCK_NAME environment variable then defaulting to
+	// "/run/pcscd/pcscd.comm".
 	SocketPath string
 }
 
+// NewClient attempts to initialize a connection with pcscd. The context is used
+// for dialing the unix domain socket.
 func NewClient(ctx context.Context, c *Config) (*Client, error) {
 	p := c.SocketPath
 	if p == "" {
@@ -180,7 +419,10 @@ func NewClient(ctx context.Context, c *Config) (*Client, error) {
 	if err != nil {
 		return nil, fmt.Errorf("dial unix socket: %v", err)
 	}
-	return &Client{
-		conn: conn,
-	}, nil
+	client := &Client{conn: conn}
+	if err := client.checkVersion(); err != nil {
+		client.Close()
+		return nil, err
+	}
+	return client, nil
 }
diff --git a/piv/internal/pcsc/pcsc_test.go b/piv/internal/pcsc/pcsc_test.go
index 46d1501..5b266a1 100644
--- a/piv/internal/pcsc/pcsc_test.go
+++ b/piv/internal/pcsc/pcsc_test.go
@@ -26,11 +26,9 @@ func TestVersion(t *testing.T) {
 	}
 	defer c.Close()
 
-	major, minor, err := c.version()
-	if err != nil {
-		t.Fatalf("getting client version: %v", err)
+	if err := c.checkVersion(); err != nil {
+		t.Fatalf("checking client client version: %v", err)
 	}
-	t.Log(major, minor)
 }
 
 func TestListReaders(t *testing.T) {
@@ -40,9 +38,100 @@ func TestListReaders(t *testing.T) {
 	}
 	defer c.Close()
 
-	readers, err := c.readers()
+	if _, err := c.Readers(); err != nil {
+		t.Fatalf("listing readers: %v", err)
+	}
+}
+
+func TestNewContext(t *testing.T) {
+	c, err := NewClient(context.Background(), &Config{})
+	if err != nil {
+		t.Fatalf("create client: %v", err)
+	}
+	defer c.Close()
+
+	ctx, err := c.NewContext()
+	if err != nil {
+		t.Fatalf("create context: %v", err)
+	}
+	if err := ctx.Close(); err != nil {
+		t.Fatalf("close context: %v", err)
+	}
+}
+
+func TestConnect(t *testing.T) {
+	c, err := NewClient(context.Background(), &Config{})
+	if err != nil {
+		t.Fatalf("create client: %v", err)
+	}
+	defer c.Close()
+
+	ctx, err := c.NewContext()
+	if err != nil {
+		t.Fatalf("create context: %v", err)
+	}
+	defer func() {
+		if err := ctx.Close(); err != nil {
+			t.Fatalf("close context: %v", err)
+		}
+	}()
+
+	readers, err := c.Readers()
 	if err != nil {
 		t.Fatalf("listing readers: %v", err)
 	}
-	t.Log(readers)
+	if len(readers) == 0 {
+		t.Skipf("no readers available for test")
+	}
+	reader := readers[0]
+
+	card, err := ctx.Connect(reader, Exclusive)
+	if err != nil {
+		t.Fatalf("new card: %v", err)
+	}
+	if err := card.Close(); err != nil {
+		t.Fatalf("close card: %v", err)
+	}
+}
+
+func TestBeginTransaction(t *testing.T) {
+	c, err := NewClient(context.Background(), &Config{})
+	if err != nil {
+		t.Fatalf("create client: %v", err)
+	}
+	defer c.Close()
+
+	ctx, err := c.NewContext()
+	if err != nil {
+		t.Fatalf("create context: %v", err)
+	}
+	defer func() {
+		if err := ctx.Close(); err != nil {
+			t.Fatalf("close context: %v", err)
+		}
+	}()
+
+	readers, err := c.Readers()
+	if err != nil {
+		t.Fatalf("listing readers: %v", err)
+	}
+	if len(readers) == 0 {
+		t.Skipf("no readers available for test")
+	}
+	reader := readers[0]
+	card, err := ctx.Connect(reader, Exclusive)
+	if err != nil {
+		t.Fatalf("new card: %v", err)
+	}
+	defer func() {
+		if err := card.Close(); err != nil {
+			t.Fatalf("close card: %v", err)
+		}
+	}()
+	if err := card.BeginTransaction(); err != nil {
+		t.Fatalf("begin transaction: %v", err)
+	}
+	if err := card.EndTransaction(); err != nil {
+		t.Fatalf("end transaction: %v", err)
+	}
 }
diff --git a/piv/pcsc_linux.go b/piv/pcsc_linux.go
index 6a5c078..18e052c 100644
--- a/piv/pcsc_linux.go
+++ b/piv/pcsc_linux.go
@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build cgo,!pcscgo
+
 package piv
 
 import "C"
diff --git a/piv/pcsc_unix.go b/piv/pcsc_unix.go
index 55d6318..fa8f5e7 100644
--- a/piv/pcsc_unix.go
+++ b/piv/pcsc_unix.go
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build cgo,!pcscgo
 // +build darwin linux freebsd
 
 package piv
diff --git a/piv/pcsc_unix_no_cgo.go b/piv/pcsc_unix_no_cgo.go
new file mode 100644
index 0000000..4a717ba
--- /dev/null
+++ b/piv/pcsc_unix_no_cgo.go
@@ -0,0 +1,91 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !cgo pcscgo
+// +build linux freebsd
+
+package piv
+
+import (
+	"context"
+	"errors"
+
+	"github.com/go-piv/piv-go/piv/internal/pcsc"
+)
+
+func scCheck(err error) error {
+	var e *pcsc.RVError
+	if errors.As(err, &e) {
+		return &scErr{int64(e.RV)}
+	}
+	return err
+}
+
+const rcSuccess = pcsc.RVSuccess
+
+type scContext struct {
+	client *pcsc.Client
+	ctx    *pcsc.Context
+}
+
+func newSCContext() (*scContext, error) {
+	c, err := pcsc.NewClient(context.Background(), &pcsc.Config{})
+	if err != nil {
+		return nil, err
+	}
+	ctx, err := c.NewContext(pcsc.Exclusive)
+	if err != nil {
+		c.Close()
+		return nil, err
+	}
+	return &scContext{c, ctx}, nil
+}
+
+func (c *scContext) Close() error {
+	err1 := c.ctx.Close()
+	if err := c.client.Close(); err != nil {
+		return err
+	}
+	return err1
+}
+
+func (c *scContext) ListReaders() ([]string, error) {
+	return c.client.Readers()
+}
+
+type scHandle struct {
+}
+
+func (c *scContext) Connect(reader string) (*scHandle, error) {
+	return nil, nil
+}
+
+func (h *scHandle) Close() error {
+	return nil
+}
+
+type scTx struct {
+}
+
+func (h *scHandle) Begin() (*scTx, error) {
+	return nil, nil
+}
+
+func (t *scTx) Close() error {
+	return nil
+}
+
+func (t *scTx) transmit(req []byte) (more bool, b []byte, err error) {
+	return false, nil, nil
+}