Print out client/server update notice even from dtail server 4 to dtail

client 3.

5 files changed, 31 insertions, 16 deletions

diff --git a/TODO.md b/TODO.md
index 435d153..2563ae7 100644
--- a/TODO.md
+++ b/TODO.md
@@ -9,7 +9,8 @@ This is a loose list of what to do. Maybe for the next releae or maybe for a lat
 [x] Have different color conf sections (by REMOTE, CLIENT, SERVER)
 [x] Paint ^CLIENT messages (e.g. use yellow backgrounds here)
 [x] Paint ^SERVER messages (e.g. use cyan backgrounds here)
+[ ] Adjust dmap with color schemas
 [ ] Fix JSONSchema for the colors
 [ ] Implement Benchmark cat-ing a file and compare to prev version.
-[ ] Client 4.x should print a warning when trying to connect to a 3.x server.
+[x] Client 4.x should print a warning when trying to connect to a 3.x server.
 [ ] Update docs for color configuration
diff --git a/internal/clients/handlers/basehandler.go b/internal/clients/handlers/basehandler.go
index fe83faa..63ceaac 100644
--- a/internal/clients/handlers/basehandler.go
+++ b/internal/clients/handlers/basehandler.go
@@ -56,7 +56,7 @@ func (h *baseHandler) SendMessage(command string) error {
 // Read data from the dtail server via Writer interface.
 func (h *baseHandler) Write(p []byte) (n int, err error) {
 	for _, b := range p {
-		if b == protocol.MessageDelimiter {
+		if b == protocol.MessageDelimiter || b == '\n' {
 			if len(h.receiveBuf) == 0 {
 				continue
 			}
diff --git a/internal/config/client.go b/internal/config/client.go
index 837c7d6..8bde7a4 100644
--- a/internal/config/client.go
+++ b/internal/config/client.go
@@ -127,8 +127,8 @@ func newDefaultClientConfig() *ClientConfig {
 				HostnameBg:    color.BgYellow,
 				HostnameFg:    color.FgBlack,
 				TextAttr:      color.AttrNone,
-				TextBg:        color.BgYellow,
-				TextFg:        color.FgBlack,
+				TextBg:        color.BgBlack,
+				TextFg:        color.FgWhite,
 			},
 			Server: serverTermColors{
 				DelimiterAttr: color.AttrDim,
@@ -151,9 +151,9 @@ func newDefaultClientConfig() *ClientConfig {
 				SeverityFatalAttr: color.AttrBlink,
 				SeverityFatalBg:   color.BgRed,
 				SeverityFatalFg:   color.FgWhite,
-				SeverityWarnAttr:  color.AttrNone,
+				SeverityWarnAttr:  color.AttrBold,
 				SeverityWarnBg:    color.BgBlack,
-				SeverityWarnFg:    color.FgRed,
+				SeverityWarnFg:    color.FgWhite,
 			},
 		},
 	}
diff --git a/internal/protocol/protocol.go b/internal/protocol/protocol.go
index e92ec6a..d3035e4 100644
--- a/internal/protocol/protocol.go
+++ b/internal/protocol/protocol.go
@@ -7,8 +7,6 @@ const (
 	MessageDelimiter byte = '¬'
 	// FieldDelimiter delimits aggregation fields.
 	FieldDelimiter string = "|"
-	// Arrow for multiple purposes
-	Arrow string = "➔"
 	// AggregateDelimiter delimits parts of an aggregation message.
-	AggregateDelimiter string = Arrow
+	AggregateDelimiter string = "➔"
 )
diff --git a/internal/server/handlers/serverhandler.go b/internal/server/handlers/serverhandler.go
index 14fc5d0..14f46a3 100644
--- a/internal/server/handlers/serverhandler.go
+++ b/internal/server/handlers/serverhandler.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -167,9 +168,9 @@ func (h *ServerHandler) handleCommand(commandStr string) {
 	logger.Debug(h.user, commandStr)
 	ctx := context.Background()
 
-	args, argc, err := h.handleProtocolVersion(strings.Split(commandStr, " "))
+	args, argc, add, err := h.handleProtocolVersion(strings.Split(commandStr, " "))
 	if err != nil {
-		h.send(h.serverMessages, logger.Error(h.user, err))
+		h.send(h.serverMessages, logger.Error(h.user, err)+add)
 		return
 	}
 
@@ -193,19 +194,34 @@ func (h *ServerHandler) handleCommand(commandStr string) {
 	h.handleUserCommand(ctx, argc, args)
 }
 
-func (h *ServerHandler) handleProtocolVersion(args []string) ([]string, int, error) {
+func (h *ServerHandler) handleProtocolVersion(args []string) ([]string, int, string, error) {
 	argc := len(args)
+	var add string
 
 	if argc <= 2 || args[0] != "protocol" {
-		return args, argc, errors.New("unable to determine protocol version")
+		return args, argc, add, errors.New("unable to determine protocol version")
 	}
 
 	if args[1] != protocol.ProtocolCompat {
-		err := fmt.Errorf("server with protocol version '%s' but client with '%s', please update DTail", protocol.ProtocolCompat, args[1])
-		return args, argc, err
+		clientCompat, _ := strconv.Atoi(args[1])
+		serverCompat, _ := strconv.Atoi(protocol.ProtocolCompat)
+		if clientCompat <= 3 {
+			// Protocol version 3 or lower expect a newline as message separator
+			// One day (after 2 major versions) this exception may be removed!
+			add = "\n"
+		}
+
+		toUpdate := "client"
+		if clientCompat > serverCompat {
+			toUpdate = "server"
+		}
+
+		err := fmt.Errorf("DTail server protocol version '%s' does not match client protocol version '%s', please update DTail %s!",
+			protocol.ProtocolCompat, args[1], toUpdate)
+		return args, argc, add, err
 	}
 
-	return args[2:], argc - 2, nil
+	return args[2:], argc - 2, add, nil
 }
 
 func (h *ServerHandler) handleBase64(args []string, argc int) ([]string, int, error) {