diff --git a/doc/funcref.sgml b/doc/funcref.sgml
index 2a6d77adc..5fa1720e4 100644
--- a/doc/funcref.sgml
+++ b/doc/funcref.sgml
@@ -435,6 +435,16 @@ see also <tt>testcode/lib/em-test.c</tt> and <tt>samples/multidemo.c</tt>.
(incomplete)
+<sect1><tt/inet.h/<label id="inet.h"><p>
+
+<itemize>
+<item><ref id="htonl" name="htonl">
+<item><ref id="htons" name="htons">
+<item><ref id="ntohl" name="ntohl">
+<item><ref id="ntohs" name="ntohs">
+</itemize>
+
+
<sect1><tt/geos.h/<label id="geos.h"><p>
<url url="geos.html" name="GEOS API">.
@@ -4388,6 +4398,45 @@ to undefined behaviour.
</descrip>
</quote>
+<sect1>htonl<label id="htonl"><p>
+
+<quote>
+<descrip>
+<tag/Function/Swaps byte order in a 32 bit word.
+<tag/Header/<tt/<ref id="inet.h" name="arpa/inet.h">/
+<tag/Declaration/<tt/int htonl(val)/
+<tag/Description/Converts a 32 bit word from from network byte order
+(big endian) to little endian (or vice-versa).
+<tag/Notes/<itemize>
+<item>The function is only available as fastcall function, so it may only
+be used in presence of a prototype.
+</itemize>
+<tag/See also/
+<ref id="ntohl" name="ntohl">
+<tag/Availability/cc65
+</descrip>
+</quote>
+
+
+<sect1>htons<label id="htons"><p>
+
+<quote>
+<descrip>
+<tag/Function/Swaps byte order in a 16 bit word.
+<tag/Header/<tt/<ref id="inet.h" name="arpa/inet.h">/
+<tag/Declaration/<tt/int htons(val)/
+<tag/Description/Converts a 16 bit word from from network byte order
+(big endian) to little endian (or vice-versa) by swapping both its bytes.
+<tag/Notes/<itemize>
+<item>The function is only available as fastcall function, so it may only
+be used in presence of a prototype.
+</itemize>
+<tag/See also/
+<ref id="ntohs" name="ntohs">
+<tag/Availability/cc65
+</descrip>
+</quote>
+
<sect1>isalnum<label id="isalnum"><p>
@@ -5757,6 +5806,44 @@ memory allocated for the driver.
</descrip>
</quote>
+<sect1>ntohl<label id="ntohl"><p>
+
+<quote>
+<descrip>
+<tag/Function/Swaps byte order in a 32 bit word.
+<tag/Header/<tt/<ref id="inet.h" name="arpa/inet.h">/
+<tag/Declaration/<tt/int __fastcall__ ntohl (int val);/
+<tag/Description/Converts a 32 bit word from from host byte order (little endian)
+to big endian (or vice-versa).
+<tag/Notes/<itemize>
+<item>The function is only available as fastcall function, so it may only
+be used in presence of a prototype.
+</itemize>
+<tag/See also/
+<ref id="htonl" name="htonl">
+<tag/Availability/cc65
+</descrip>
+</quote>
+
+<sect1>ntohs<label id="ntohs"><p>
+
+<quote>
+<descrip>
+<tag/Function/Swaps byte order in a 16 bit word.
+<tag/Header/<tt/<ref id="inet.h" name="arpa/inet.h">/
+<tag/Declaration/<tt/int __fastcall__ ntohs (int val);/
+<tag/Description/Converts a 16 bit word from from host byte order (little endian)
+to big endian (or vice-versa) by swapping both its bytes.
+<tag/Notes/<itemize>
+<item>The function is only available as fastcall function, so it may only
+be used in presence of a prototype.
+</itemize>
+<tag/See also/
+<ref id="htons" name="htons">
+<tag/Availability/cc65
+</descrip>
+</quote>
+
<sect1>offsetof<label id="offsetof"><p>
<quote>
diff --git a/include/arpa/inet.h b/include/arpa/inet.h
new file mode 100644
index 000000000..cd353a2bb
--- /dev/null
+++ b/include/arpa/inet.h
@@ -0,0 +1,67 @@
+/*****************************************************************************/
+/* */
+/* arpa/inet.h */
+/* */
+/* Endianness utilities for cc65 */
+/* */
+/* */
+/* */
+/* (C) 2023 Colin Leroy-Mira, <colin@colino.net> */
+/* */
+/* */
+/* This software is provided 'as-is', without any expressed or implied */
+/* warranty. In no event will the authors be held liable for any damages */
+/* arising from the use of this software. */
+/* */
+/* Permission is granted to anyone to use this software for any purpose, */
+/* including commercial applications, and to alter it and redistribute it */
+/* freely, subject to the following restrictions: */
+/* */
+/* 1. The origin of this software must not be misrepresented; you must not */
+/* claim that you wrote the original software. If you use this software */
+/* in a product, an acknowledgment in the product documentation would be */
+/* appreciated but is not required. */
+/* 2. Altered source versions must be plainly marked as such, and must not */
+/* be misrepresented as being the original software. */
+/* 3. This notice may not be removed or altered from any source */
+/* distribution. */
+/* */
+/*****************************************************************************/
+
+
+
+#ifndef _ARPA_INET_H
+#define _ARPA_INET_H
+
+
+
+/*****************************************************************************/
+/* Code */
+/*****************************************************************************/
+
+
+
+#if (__OPT_i__ < 200)
+int __fastcall__ ntohs (int val);
+int __fastcall__ htons (int val);
+#else
+
+#define ntohs(x) \
+ ( \
+ __AX__=(x), \
+ asm("sta tmp1"), \
+ asm("txa"), \
+ asm("ldx tmp1"), \
+ __AX__ \
+ )
+#define htons(x) ntohs(x)
+
+#endif
+
+long __fastcall__ ntohl (long val);
+long __fastcall__ htonl (long val);
+
+
+
+/* End of arpa/inet.h */
+#endif
diff --git a/libsrc/common/ntohl.s b/libsrc/common/ntohl.s
new file mode 100644
index 000000000..77adba253
--- /dev/null
+++ b/libsrc/common/ntohl.s
@@ -0,0 +1,32 @@
+;
+; Colin Leroy-Mira <colin@colino.net>, 2023-09-06
+;
+; int __fastcall__ ntohl (long val);
+;
+
+.export _ntohl, _htonl
+.import popa
+.importzp tmp1, tmp2, sreg
+
+_htonl := _ntohl
+
+_ntohl:
+ ; The parts of our 32 bit word
+ ; are in sreg+1, sreg, X, A.
+
+ ; Save A and X
+ stx tmp1
+ sta tmp2
+
+ ; Invert high word
+ lda sreg+1
+ ldx sreg
+
+ ; Invert low word
+ ldy tmp1
+ sty sreg
+
+ ldy tmp2
+ sty sreg+1
+
+ rts
diff --git a/libsrc/common/ntohs.s b/libsrc/common/ntohs.s
new file mode 100644
index 000000000..042ddb005
--- /dev/null
+++ b/libsrc/common/ntohs.s
@@ -0,0 +1,16 @@
+;
+; Colin Leroy-Mira <colin@colino.net>, 2023-09-06
+;
+; int __fastcall__ ntohs (int val);
+;
+
+.export _ntohs, _htons
+.importzp tmp1
+
+_htons := _ntohs
+
+_ntohs:
+ sta tmp1
+ txa
+ ldx tmp1
+ rts
diff --git a/test/val/lib_common_htonl.c b/test/val/lib_common_htonl.c
new file mode 100644
index 000000000..53a210a84
--- /dev/null
+++ b/test/val/lib_common_htonl.c
@@ -0,0 +1,34 @@
+/*
+ !!DESCRIPTION!! A small test for htons.
+ !!ORIGIN!!
+ !!LICENCE!!
+ !!AUTHOR!! Colin Leroy-Mira
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <arpa/inet.h>
+
+static unsigned int Failures = 0;
+
+static void CheckHtonl (long input, long expected)
+{
+ long result = htonl(input);
+ if (result != expected) {
+ printf ("htonl error:\n"
+ " result = %ld for %ld, should be %ld\n", result, input, expected);
+ ++Failures;
+ }
+}
+
+int main (void)
+{
+ CheckHtonl(0x00000000, 0x00000000);
+ CheckHtonl(0x12345678, 0x78563412);
+ CheckHtonl(0xAABBCCDD, 0xDDCCBBAA);
+ CheckHtonl(0xFFFFFFFF, 0xFFFFFFFF);
+
+ printf ("Failures: %u\n", Failures);
+
+ return Failures;
+}
diff --git a/test/val/lib_common_htons.c b/test/val/lib_common_htons.c
new file mode 100644
index 000000000..42bbb3d6b
--- /dev/null
+++ b/test/val/lib_common_htons.c
@@ -0,0 +1,34 @@
+/*
+ !!DESCRIPTION!! A small test for htons.
+ !!ORIGIN!!
+ !!LICENCE!!
+ !!AUTHOR!! Colin Leroy-Mira
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <arpa/inet.h>
+
+static unsigned int Failures = 0;
+
+static void CheckHtons (int input, int expected)
+{
+ int result = htons(input);
+ if (result != expected) {
+ printf ("htons error:\n"
+ " result = %d for %d, should be %d\n", result, input, expected);
+ ++Failures;
+ }
+}
+
+int main (void)
+{
+ CheckHtons(0x0000, 0x0000);
+ CheckHtons(0x1234, 0x3412);
+ CheckHtons(0xA0F2, 0xF2A0);
+ CheckHtons(0xFFFF, 0xFFFF);
+
+ printf ("Failures: %u\n", Failures);
+
+ return Failures;
+}