diff --git a/cmd/adb/main.go b/cmd/adb/main.go
index 2dfddf2..48f7655 100644
--- a/cmd/adb/main.go
+++ b/cmd/adb/main.go
@@ -27,9 +27,9 @@ var (
 	pullRemoteArg    = pullCommand.Arg("remote", "Path of source file on device.").Required().String()
 	pullLocalArg     = pullCommand.Arg("local", "Path of destination file.").String()
 
-	pushCommand      = kingpin.Command("push", "Push a file to the device.").Hidden()
+	pushCommand      = kingpin.Command("push", "Push a file to the device.")
 	pushProgressFlag = pushCommand.Flag("progress", "Show progress.").Short('p').Bool()
-	pushLocalArg     = pushCommand.Arg("local", "Path of source file.").Required().String()
+	pushLocalArg     = pushCommand.Arg("local", "Path of source file.").Required().File()
 	pushRemoteArg    = pushCommand.Arg("remote", "Path of destination file on device.").Required().String()
 )
 
@@ -143,47 +143,70 @@ func pull(showProgress bool, remotePath, localPath string, device goadb.DeviceDe
 	}
 	defer localFile.Close()
 
-	var output io.Writer
-	var updateProgress func()
+	if err := copyWithProgressAndStats(localFile, remoteFile, int(info.Size), showProgress); err != nil {
+		fmt.Fprintln(os.Stderr, "error pulling file:", err)
+		return 1
+	}
+	return 0
+}
+
+func push(showProgress bool, localFile *os.File, remotePath string, device goadb.DeviceDescriptor) int {
+	if remotePath == "" {
+		fmt.Fprintln(os.Stderr, "error: must specify remote file")
+		kingpin.Usage()
+		return 1
+	}
+
+	client := goadb.NewDeviceClient(goadb.ClientConfig{}, device)
+
+	info, err := os.Stat(localFile.Name())
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error reading local file %s: %s\n", localFile.Name(), err)
+		return 1
+	}
+
+	writer, err := client.OpenWrite(remotePath, info.Mode(), info.ModTime())
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error opening remote file %s: %s\n", remotePath, err)
+		return 1
+	}
+	defer writer.Close()
+
+	if err := copyWithProgressAndStats(writer, localFile, int(info.Size()), showProgress); err != nil {
+		fmt.Fprintln(os.Stderr, "error pushing file:", err)
+		return 1
+	}
+	return 0
+}
+
+func copyWithProgressAndStats(dst io.Writer, src io.Reader, size int, showProgress bool) error {
+	var progress *pb.ProgressBar
 	if showProgress {
-		output, updateProgress = createProgressBarWriter(int(info.Size), localFile)
-	} else {
-		output = localFile
-		updateProgress = func() {}
+		progress = pb.New(size)
+		progress.SetUnits(pb.U_BYTES)
+		progress.SetRefreshRate(100 * time.Millisecond)
+		progress.ShowSpeed = true
+		progress.ShowPercent = true
+		progress.ShowTimeLeft = true
+		progress.Start()
+		dst = io.MultiWriter(dst, progress)
 	}
 
 	startTime := time.Now()
-	copied, err := io.Copy(output, remoteFile)
+	copied, err := io.Copy(dst, src)
 
-	// Force progress update if the transfer was really fast.
-	updateProgress()
+	if progress != nil {
+		// Force progress update if the transfer was really fast.
+		progress.Update()
+	}
 
 	if err != nil {
-		fmt.Fprintln(os.Stderr, "error pulling file:", err)
-		return 1
+		return err
 	}
 
 	duration := time.Now().Sub(startTime)
 	rate := int64(float64(copied) / duration.Seconds())
 	fmt.Printf("%d B/s (%d bytes in %s)\n", rate, copied, duration)
-	return 0
-}
 
-func push(showProgress bool, localPath, remotePath string, device goadb.DeviceDescriptor) int {
-	fmt.Fprintln(os.Stderr, "not implemented")
-	return 1
-}
-
-func createProgressBarWriter(size int, w io.Writer) (progressWriter io.Writer, update func()) {
-	progress := pb.New(size)
-	progress.SetUnits(pb.U_BYTES)
-	progress.SetRefreshRate(100 * time.Millisecond)
-	progress.ShowSpeed = true
-	progress.ShowPercent = true
-	progress.ShowTimeLeft = true
-	progress.Start()
-
-	progressWriter = io.MultiWriter(w, progress)
-	update = progress.Update
-	return
+	return nil
 }
diff --git a/device_client.go b/device_client.go
index d69102f..ed2598c 100644
--- a/device_client.go
+++ b/device_client.go
@@ -3,12 +3,18 @@ package goadb
 import (
 	"fmt"
 	"io"
+	"os"
 	"strings"
+	"time"
 
 	"github.com/zach-klippenstein/goadb/util"
 	"github.com/zach-klippenstein/goadb/wire"
 )
 
+// MtimeOfClose should be passed to OpenWrite to set the file modification time to the time the Close
+// method is called.
+var MtimeOfClose = time.Time{}
+
 // DeviceClient communicates with a specific Android device.
 type DeviceClient struct {
 	config     ClientConfig
@@ -171,6 +177,20 @@ func (c *DeviceClient) OpenRead(path string) (io.ReadCloser, error) {
 	return reader, wrapClientError(err, c, "OpenRead(%s)", path)
 }
 
+// OpenWrite opens the file at path on the device, creating it with the permissions specified
+// by perms if necessary, and returns a writer that writes to the file.
+// The files modification time will be set to mtime when the WriterCloser is closed. The zero value
+// is TimeOfClose, which will use the time the Close method is called as the modification time.
+func (c *DeviceClient) OpenWrite(path string, perms os.FileMode, mtime time.Time) (io.WriteCloser, error) {
+	conn, err := c.getSyncConn()
+	if err != nil {
+		return nil, wrapClientError(err, c, "OpenWrite(%s)", path)
+	}
+
+	writer, err := sendFile(conn, path, perms, mtime)
+	return writer, wrapClientError(err, c, "OpenWrite(%s)", path)
+}
+
 // getAttribute returns the first message returned by the server by running
 // <host-prefix>:<attr>, where host-prefix is determined from the DeviceDescriptor.
 func (c *DeviceClient) getAttribute(attr string) (string, error) {
diff --git a/sync_client.go b/sync_client.go
index c3497d6..75dfdd4 100644
--- a/sync_client.go
+++ b/sync_client.go
@@ -1,4 +1,3 @@
-// TODO(z): Implement send.
 package goadb
 
 import (
@@ -16,7 +15,7 @@ func stat(conn *wire.SyncConn, path string) (*DirEntry, error) {
 	if err := conn.SendOctetString("STAT"); err != nil {
 		return nil, err
 	}
-	if err := conn.SendString(path); err != nil {
+	if err := conn.SendBytes([]byte(path)); err != nil {
 		return nil, err
 	}
 
@@ -35,7 +34,7 @@ func listDirEntries(conn *wire.SyncConn, path string) (entries *DirEntries, err
 	if err = conn.SendOctetString("LIST"); err != nil {
 		return
 	}
-	if err = conn.SendString(path); err != nil {
+	if err = conn.SendBytes([]byte(path)); err != nil {
 		return
 	}
 
@@ -46,12 +45,29 @@ func receiveFile(conn *wire.SyncConn, path string) (io.ReadCloser, error) {
 	if err := conn.SendOctetString("RECV"); err != nil {
 		return nil, err
 	}
-	if err := conn.SendString(path); err != nil {
+	if err := conn.SendBytes([]byte(path)); err != nil {
 		return nil, err
 	}
 	return newSyncFileReader(conn)
 }
 
+// sendFile returns a WriteCloser than will write to the file at path on device.
+// The file will be created with permissions specified by mode.
+// The file's modified time will be set to mtime, unless mtime is 0, in which case the time the writer is
+// closed will be used.
+func sendFile(conn *wire.SyncConn, path string, mode os.FileMode, mtime time.Time) (io.WriteCloser, error) {
+	if err := conn.SendOctetString("SEND"); err != nil {
+		return nil, err
+	}
+
+	pathAndMode := encodePathAndMode(path, mode)
+	if err := conn.SendBytes(pathAndMode); err != nil {
+		return nil, err
+	}
+
+	return newSyncFileWriter(conn, mtime), nil
+}
+
 func readStat(s wire.SyncScanner) (entry *DirEntry, err error) {
 	mode, err := s.ReadFileMode()
 	if err != nil {
diff --git a/sync_file_writer.go b/sync_file_writer.go
new file mode 100644
index 0000000..35130df
--- /dev/null
+++ b/sync_file_writer.go
@@ -0,0 +1,76 @@
+package goadb
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/zach-klippenstein/goadb/util"
+	"github.com/zach-klippenstein/goadb/wire"
+)
+
+// syncFileWriter wraps a SyncConn that has requested to send a file.
+type syncFileWriter struct {
+	// The modification time to write in the footer.
+	// If 0, use the current time.
+	mtime time.Time
+
+	// Reader used to read data from the adb connection.
+	sender wire.SyncSender
+}
+
+var _ io.WriteCloser = &syncFileWriter{}
+
+func newSyncFileWriter(s wire.SyncSender, mtime time.Time) io.WriteCloser {
+	return &syncFileWriter{
+		mtime:  mtime,
+		sender: s,
+	}
+}
+
+/*
+encodePathAndMode encodes a path and file mode as required for starting a send file stream.
+
+From https://android.googlesource.com/platform/system/core/+/master/adb/SYNC.TXT:
+	The remote file name is split into two parts separated by the last
+	comma (","). The first part is the actual path, while the second is a decimal
+	encoded file mode containing the permissions of the file on device.
+*/
+func encodePathAndMode(path string, mode os.FileMode) []byte {
+	return []byte(fmt.Sprintf("%s,%d", path, uint32(mode.Perm())))
+}
+
+// Write writes the min of (len(buf), 64k).
+func (w *syncFileWriter) Write(buf []byte) (n int, err error) {
+	// Writes < 64k have a one-to-one mapping to chunks.
+	// If buffer is larger than the max, we'll return the max size and leave it up to the
+	// caller to handle correctly.
+	if len(buf) > wire.SyncMaxChunkSize {
+		buf = buf[:wire.SyncMaxChunkSize]
+	}
+
+	if err := w.sender.SendOctetString(wire.StatusSyncData); err != nil {
+		return 0, err
+	}
+	if err := w.sender.SendBytes(buf); err != nil {
+		return 0, err
+	}
+
+	return len(buf), nil
+}
+
+func (w *syncFileWriter) Close() error {
+	if w.mtime.IsZero() {
+		w.mtime = time.Now()
+	}
+
+	if err := w.sender.SendOctetString(wire.StatusSyncDone); err != nil {
+		return util.WrapErrf(err, "error closing file writer")
+	}
+	if err := w.sender.SendTime(w.mtime); err != nil {
+		return util.WrapErrf(err, "error writing file modification time")
+	}
+
+	return util.WrapErrf(w.sender.Close(), "error closing FileWriter")
+}
diff --git a/sync_file_writer_test.go b/sync_file_writer_test.go
new file mode 100644
index 0000000..1317ef1
--- /dev/null
+++ b/sync_file_writer_test.go
@@ -0,0 +1,93 @@
+package goadb
+
+import (
+	"bytes"
+	"testing"
+	"time"
+
+	"encoding/binary"
+	"strings"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/zach-klippenstein/goadb/wire"
+)
+
+func TestFileWriterWriteSingleChunk(t *testing.T) {
+	var buf bytes.Buffer
+	writer := newSyncFileWriter(wire.NewSyncSender(&buf), MtimeOfClose)
+
+	n, err := writer.Write([]byte("hello"))
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	assert.Equal(t, "DATA\005\000\000\000hello", buf.String())
+}
+
+func TestFileWriterWriteMultiChunk(t *testing.T) {
+	var buf bytes.Buffer
+	writer := newSyncFileWriter(wire.NewSyncSender(&buf), MtimeOfClose)
+
+	n, err := writer.Write([]byte("hello"))
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	n, err = writer.Write([]byte(" world"))
+	assert.NoError(t, err)
+	assert.Equal(t, 6, n)
+
+	assert.Equal(t, "DATA\005\000\000\000helloDATA\006\000\000\000 world", buf.String())
+}
+
+func TestFileWriterWriteLargeChunk(t *testing.T) {
+	var buf bytes.Buffer
+	writer := newSyncFileWriter(wire.NewSyncSender(&buf), MtimeOfClose)
+
+	data := make([]byte, wire.SyncMaxChunkSize+1)
+	n, err := writer.Write(data)
+
+	assert.NoError(t, err)
+	assert.Equal(t, wire.SyncMaxChunkSize, n)
+	assert.Equal(t, 8 + wire.SyncMaxChunkSize, buf.Len())
+
+	expectedHeader := []byte("DATA0000")
+	binary.LittleEndian.PutUint32(expectedHeader[4:], wire.SyncMaxChunkSize)
+	assert.Equal(t, expectedHeader, buf.Bytes()[:8])
+
+	assert.Equal(t, string(data[:wire.SyncMaxChunkSize]), buf.String()[8:])
+}
+
+func TestFileWriterCloseEmpty(t *testing.T) {
+	var buf bytes.Buffer
+	mtime := time.Unix(1, 0)
+	writer := newSyncFileWriter(wire.NewSyncSender(&buf), mtime)
+
+	assert.NoError(t, writer.Close())
+
+	assert.Equal(t, "DONE\x01\x00\x00\x00", buf.String())
+}
+
+func TestFileWriterWriteClose(t *testing.T) {
+	var buf bytes.Buffer
+	mtime := time.Unix(1, 0)
+	writer := newSyncFileWriter(wire.NewSyncSender(&buf), mtime)
+
+	writer.Write([]byte("hello"))
+	assert.NoError(t, writer.Close())
+
+	assert.Equal(t, "DATA\005\000\000\000helloDONE\x01\x00\x00\x00", buf.String())
+}
+
+func TestFileWriterCloseAutoMtime(t *testing.T) {
+	var buf bytes.Buffer
+	writer := newSyncFileWriter(wire.NewSyncSender(&buf), MtimeOfClose)
+
+	assert.NoError(t, writer.Close())
+	assert.Len(t, buf.String(), 8)
+	assert.True(t, strings.HasPrefix(buf.String(), "DONE"))
+
+	mtimeBytes := buf.Bytes()[4:]
+	mtimeActual := time.Unix(int64(binary.LittleEndian.Uint32(mtimeBytes)), 0)
+
+	// Delta has to be a whole second since adb only supports second granularity for mtimes.
+	assert.WithinDuration(t, time.Now(), mtimeActual, 1*time.Second)
+}
diff --git a/util/error.go b/util/error.go
index e065899..9246fe6 100644
--- a/util/error.go
+++ b/util/error.go
@@ -77,6 +77,44 @@ func WrapErrf(cause error, format string, args ...interface{}) error {
 	}
 }
 
+// CombineErrs returns an error that wraps all the non-nil errors passed to it.
+// If all errors are nil, returns nil.
+// If there's only one non-nil error, returns that error without wrapping.
+// Else, returns an error with the message and code as passed, with the cause set to an error
+// that contains all the non-nil errors and for which Error() returns the concatenation of all their messages.
+func CombineErrs(msg string, code ErrCode, errs ...error) error {
+	var nonNilErrs []error
+	for _, err := range errs {
+		if err != nil {
+			nonNilErrs = append(nonNilErrs, err)
+		}
+	}
+
+	switch len(nonNilErrs) {
+	case 0:
+		return nil
+	case 1:
+		return nonNilErrs[0]
+	default:
+		return WrapErrorf(multiError(nonNilErrs), code, "%s", msg)
+	}
+}
+
+type multiError []error
+
+func (errs multiError) Error() string {
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, "%d errors: [", len(errs))
+	for i, err := range errs {
+		buf.WriteString(err.Error())
+		if i < len(errs)-1 {
+			buf.WriteString(" ∪ ")
+		}
+	}
+	buf.WriteRune(']')
+	return buf.String()
+}
+
 /*
 WrapErrorf returns an *Err that wraps another arbitrary error with an ErrCode and a message.
 
diff --git a/util/error_test.go b/util/error_test.go
index 2e629db..bc902d6 100644
--- a/util/error_test.go
+++ b/util/error_test.go
@@ -24,3 +24,19 @@ caused by err3`
 
 	assert.Equal(t, expected, ErrorWithCauseChain(err))
 }
+
+func TestCombineErrors(t *testing.T) {
+	assert.NoError(t, CombineErrs("hello", AdbError))
+	assert.NoError(t, CombineErrs("hello", AdbError, nil, nil))
+
+	err1 := errors.New("lulz")
+	err2 := errors.New("fail")
+
+	err := CombineErrs("hello", AdbError, nil, err1, nil)
+	assert.EqualError(t, err, "lulz")
+
+	err = CombineErrs("hello", AdbError, err1, err2)
+	assert.EqualError(t, err, "AdbError: hello")
+	assert.Equal(t, `AdbError: hello
+caused by 2 errors: [lulz ∪ fail]`, ErrorWithCauseChain(err))
+}
diff --git a/wire/sync_conn.go b/wire/sync_conn.go
index 521efc0..1752a09 100644
--- a/wire/sync_conn.go
+++ b/wire/sync_conn.go
@@ -1,9 +1,10 @@
-// TODO(z): Write SyncSender.SendBytes().
 package wire
 
+import "github.com/zach-klippenstein/goadb/util"
+
 const (
 	// Chunks cannot be longer than 64k.
-	MaxChunkSize = 64 * 1024
+	SyncMaxChunkSize = 64 * 1024
 )
 
 /*
@@ -28,3 +29,9 @@ type SyncConn struct {
 	SyncScanner
 	SyncSender
 }
+
+// Close closes both the sender and the scanner, and returns any errors.
+func (c SyncConn) Close() error {
+	return util.CombineErrs("error closing SyncConn", util.NetworkError,
+		c.SyncScanner.Close(), c.SyncSender.Close())
+}
diff --git a/wire/sync_sender.go b/wire/sync_sender.go
index 15dfde8..9189080 100644
--- a/wire/sync_sender.go
+++ b/wire/sync_sender.go
@@ -10,14 +10,17 @@ import (
 )
 
 type SyncSender interface {
+	io.Closer
+
 	// SendOctetString sends a 4-byte string.
 	SendOctetString(string) error
 	SendInt32(int32) error
 	SendFileMode(os.FileMode) error
 	SendTime(time.Time) error
 
-	// Sends len(bytes) as an octet, followed by bytes.
-	SendString(str string) error
+	// Sends len(data) as an octet, followed by the bytes.
+	// If data is bigger than SyncMaxChunkSize, it returns an assertion error.
+	SendBytes(data []byte) error
 }
 
 type realSyncSender struct {
@@ -54,17 +57,24 @@ func (s *realSyncSender) SendTime(t time.Time) error {
 		util.NetworkError, "error sending time on sync sender")
 }
 
-func (s *realSyncSender) SendString(str string) error {
-	length := len(str)
-	if length > MaxChunkSize {
+func (s *realSyncSender) SendBytes(data []byte) error {
+	length := len(data)
+	if length > SyncMaxChunkSize {
 		// This limit might not apply to filenames, but it's big enough
 		// that I don't think it will be a problem.
-		return util.AssertionErrorf("str must be <= %d in length", MaxChunkSize)
+		return util.AssertionErrorf("data must be <= %d in length", SyncMaxChunkSize)
 	}
 
 	if err := s.SendInt32(int32(length)); err != nil {
-		return util.WrapErrorf(err, util.NetworkError, "error sending string length on sync sender")
+		return util.WrapErrorf(err, util.NetworkError, "error sending data length on sync sender")
 	}
-	return util.WrapErrorf(writeFully(s.Writer, []byte(str)),
-		util.NetworkError, "error sending string on sync sender")
+	return util.WrapErrorf(writeFully(s.Writer, data),
+		util.NetworkError, "error sending data on sync sender")
+}
+
+func (s *realSyncSender) Close() error {
+	if closer, ok := s.Writer.(io.Closer); ok {
+		return util.WrapErrorf(closer.Close(), util.NetworkError, "error closing sync sender")
+	}
+	return nil
 }
diff --git a/wire/sync_test.go b/wire/sync_test.go
index 2c928fb..5321639 100644
--- a/wire/sync_test.go
+++ b/wire/sync_test.go
@@ -60,10 +60,10 @@ func TestSyncReadStringTooShort(t *testing.T) {
 	assert.Equal(t, errIncompleteMessage("bytes", 1, 5), err)
 }
 
-func TestSyncSendString(t *testing.T) {
+func TestSyncSendBytes(t *testing.T) {
 	var buf bytes.Buffer
 	s := NewSyncSender(&buf)
-	err := s.SendString("hello")
+	err := s.SendBytes([]byte("hello"))
 	assert.NoError(t, err)
 	assert.Equal(t, "\005\000\000\000hello", buf.String())
 }