diff --git a/CHANGELOG b/CHANGELOG
index 2335411..183ed68 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -21,6 +21,8 @@ CHANGES:
 	- iodine client now shuts down if it detects a server restart.
 	- iodined now replies to NS request on its own domain, fixes issue #33.
 		The destination IP address is sent as reply.
+	- Upstream data is now Base64 encoded if relay server preserves case and
+		supports the plus (+) character in domain names, fixes #16.
 
 2008-08-06: 0.4.2 "Opened Zone"
 	- Applied a few small patches from Maxim Bourmistrov and Gregor Herrmann
diff --git a/src/iodine.c b/src/iodine.c
index 7755f6a..c25b0ed 100644
--- a/src/iodine.c
+++ b/src/iodine.c
@@ -40,6 +40,7 @@
 #include "common.h"
 #include "encoding.h"
 #include "base32.h"
+#include "base64.h"
 #include "dns.h"
 #include "login.h"
 #include "tun.h"
@@ -146,13 +147,13 @@ build_hostname(char *buf, size_t buflen,
 	return space;
 }
 
-int
+static int
 is_sending()
 {
 	return (packet.len != 0);
 }
 
-int
+static int
 read_dns(int fd, char *buf, int buflen)
 {
 	struct sockaddr_in from;
@@ -324,7 +325,7 @@ send_chunk(int fd)
 	send_query(fd, buf);
 }
 
-void
+static void
 send_login(int fd, char *login, int len)
 {
 	char data[19];
@@ -361,7 +362,7 @@ send_ping(int fd)
 	send_packet(fd, 'P', data, sizeof(data));
 }
 
-void 
+static void 
 send_version(int fd, uint32_t version)
 {
 	char data[6];
@@ -379,15 +380,33 @@ send_version(int fd, uint32_t version)
 	send_packet(fd, 'V', data, sizeof(data));
 }
 
-void
+static void
 send_case_check(int fd)
 {
-	char buf[512] = "zZaAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyY123-4560789.";
+	/* The '+' plus character is not allowed according to RFC. 
+	 * Expect to get SERVFAIL or similar if it is rejected.
+	 */
+	char buf[512] = "zZ+-aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyY1234.";
 
 	strncat(buf, topdomain, 512 - strlen(buf));
 	send_query(fd, buf);
 }
 
+static void
+send_codec_switch(int fd, int userid, int bits)
+{
+	char buf[512] = "S00.";
+	if (userid >= 0 && userid < 9) {
+		buf[1] += userid;
+	}
+	if (bits >= 0 && bits < 9) {
+		buf[2] += bits;
+	}
+	
+	strncat(buf, topdomain, 512 - strlen(buf));
+	send_query(fd, buf);
+}
+
 static int
 handshake(int dns_fd)
 {
@@ -519,30 +538,30 @@ perform_case_check:
 		if(r > 0) {
 			read = read_dns(dns_fd, in, sizeof(in));
 			
-			if(read <= 0) {
-				warn("read");
-				continue;
-			}
-
 			if (read > 0) {
 				if (in[0] == 'z' || in[0] == 'Z') {
-					if (read < (26 * 2)) {
-						printf("Received short case reply...\n");
+					if (read < (27 * 2)) {
+						printf("Received short case check reply. Will use base32 encoder\n");
+						goto switch_codec;
 					} else {
 						int k;
 
+						/* TODO enhance this, base128 is probably also possible */
 						case_preserved = 1;
-						for (k = 0; k < 26 && case_preserved; k += 2) {
+						for (k = 0; k < 27 && case_preserved; k += 2) {
 							if (in[k] == in[k+1]) {
-								/* test string: zZaAbBcCdD... */
+								/* test string: zZ+-aAbBcCdDeE... */
 								case_preserved = 0;
 							}
 						}
-						return 0;
+						goto switch_codec;
 					}
 				} else {
 					printf("Received bad case check reply\n");
 				}
+			} else {
+				printf("Got error on case check, will use base32\n");
+				goto switch_codec;
 			}
 		}
 
@@ -550,6 +569,52 @@ perform_case_check:
 	}
 
 	printf("No reply on case check, continuing\n");
+switch_codec:
+	if (!case_preserved)
+		return 0;
+
+	dataenc = get_base64_encoder();
+	printf("Switching to %s codec\n", dataenc->name);
+	/* Send to server that this user will use base64 from now on */
+	for (i=0; running && i<5 ;i++) {
+		int bits;
+		tv.tv_sec = i + 1;
+		tv.tv_usec = 0;
+
+		bits = 6; /* base64 = 6 bits per byte */
+
+		send_codec_switch(dns_fd, userid, bits);
+		
+		FD_ZERO(&fds);
+		FD_SET(dns_fd, &fds);
+
+		r = select(dns_fd + 1, &fds, NULL, NULL, &tv);
+
+		if(r > 0) {
+			read = read_dns(dns_fd, in, sizeof(in));
+			
+			if (read > 0) {
+				if (strncmp("BADLEN", in, 6) == 0) {
+					printf("Server got bad message length. ");
+					goto codec_revert;
+				} else if (strncmp("BADIP", in, 5) == 0) {
+					printf("Server rejected sender IP address. ");
+					goto codec_revert;
+				} else if (strncmp("BADCODEC", in, 8) == 0) {
+					printf("Server rejected the selected codec. ");
+					goto codec_revert;
+				}
+				in[read] = 0; /* zero terminate */
+				printf("Server switched to codec %s\n", in);
+				return 0;
+			}
+		}
+		printf("Retrying codec switch...\n");
+	}
+	printf("No reply from server on codec switch. ");
+codec_revert: 
+	printf("Falling back to base32\n");
+	dataenc = get_base32_encoder();
 	return 0;
 }
 		
diff --git a/src/iodined.c b/src/iodined.c
index 93cfde8..cbfdcd6 100644
--- a/src/iodined.c
+++ b/src/iodined.c
@@ -44,6 +44,7 @@
 #include "dns.h"
 #include "encoding.h"
 #include "base32.h"
+#include "base64.h"
 #include "user.h"
 #include "login.h"
 #include "tun.h"
@@ -261,11 +262,43 @@ handle_null_request(int tun_fd, int dns_fd, struct query *q, int domain_len)
 		memcpy(&(users[userid].q), q, sizeof(struct query));
 		users[userid].last_pkt = time(NULL);
 	} else if(in[0] == 'Z' || in[0] == 'z') {
-		/* Case conservation check */
+		/* Check for case conservation and chars not allowed according to RFC */
 
 		/* Reply with received hostname as data */
 		write_dns(dns_fd, q, in, domain_len);
 		return;
+	} else if(in[0] == 'S' || in[0] == 's') {
+		int codec;
+		struct encoder *enc;
+		if (domain_len != 4) { /* len = 4, example: "S15." */
+			write_dns(dns_fd, q, "BADLEN", 6);
+			return;
+		}
+
+		userid = in[1] & 0x7;
+		
+		if (ip_cmp(userid, q) != 0) {
+			write_dns(dns_fd, q, "BADIP", 5);
+			return; /* illegal id */
+		}
+		
+		codec = in[2] & 0xF;
+		switch (codec) {
+		case 5: /* 5 bits per byte = base32 */
+			enc = get_base32_encoder();
+			user_switch_codec(userid, enc);
+			write_dns(dns_fd, q, enc->name, strlen(enc->name));
+			break;
+		case 6: /* 6 bits per byte = base64 */
+			enc = get_base64_encoder();
+			user_switch_codec(userid, enc);
+			write_dns(dns_fd, q, enc->name, strlen(enc->name));
+			break;
+		default:
+			write_dns(dns_fd, q, "BADCODEC", 8);
+			break;
+		}
+		return;
 	} else if((in[0] >= '0' && in[0] <= '9')
 			|| (in[0] >= 'a' && in[0] <= 'f')
 			|| (in[0] >= 'A' && in[0] <= 'F')) {
diff --git a/src/user.c b/src/user.c
index 8b242d8..6b53e56 100644
--- a/src/user.c
+++ b/src/user.c
@@ -106,3 +106,11 @@ find_available_user()
 	return ret;
 }
 
+void
+user_switch_codec(int userid, struct encoder *enc)
+{
+	if (userid < 0 || userid >= USERS)
+		return;
+	
+	users[userid].encoder = enc;
+}
diff --git a/src/user.h b/src/user.h
index 20ea3c8..fdbcef5 100644
--- a/src/user.h
+++ b/src/user.h
@@ -38,5 +38,6 @@ void init_users(in_addr_t);
 int find_user_by_ip(uint32_t);
 int all_users_waiting_to_send();
 int find_available_user();
+void user_switch_codec(int userid, struct encoder *enc);
 
 #endif