--- aseqnet.c.bak	2012-01-25 10:43:38.000000000 +0100
+++ aseqnet.c	2019-05-01 12:08:53.966228471 +0200
@@ -3,6 +3,8 @@
  *   ver.0.1
  *
  * Copyright (C) 1999-2000 Takashi Iwai
+ * Modified by Rob van der Putten, Leiden, Holland, 
+ * rob at sput dot nl.
  * 
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2 as
@@ -15,18 +17,21 @@
  *
  */
 
+#include <alsa/asoundlib.h>
+#include <arpa/inet.h>
+#include <assert.h>
+#include <ctype.h>
+#include <getopt.h>
+#include <locale.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <ctype.h>
 #include <string.h>
-#include <netinet/in.h>
 #include <sys/socket.h>
-#include <netdb.h>
-#include <locale.h>
-#include <alsa/asoundlib.h>
-#include <getopt.h>
-#include <signal.h>
-#include <assert.h>
+#include <sys/types.h>
 #include "aconfig.h"
 #include "gettext.h"
 
@@ -327,17 +332,24 @@
  */
 static void init_server(int port)
 {
+	/*
+	*       RvdP, changed to support IPv6
+	*       Dual stack only!
+	*/
 	int i;
 	int curstate = 1;
-	struct sockaddr_in addr;
+	int ipv6only = 0;
+	int nodelay  = 1;
+	int quickack = 1;
+	struct sockaddr_in6 addr;
 
 	memset(&addr, 0, sizeof(addr));
 
-	addr.sin_family = AF_INET;
-	addr.sin_addr.s_addr = INADDR_ANY;
-	addr.sin_port = htons(port);
+	addr.sin6_family = AF_INET6;
+	inet_pton(AF_INET6, "::", &(addr.sin6_addr));
+	addr.sin6_port = htons(port);
 
-	sockfd = socket(AF_INET, SOCK_STREAM, 0);
+	sockfd = socket(PF_INET6, SOCK_STREAM, 0);
 	if (sockfd < 0)  {
 		perror("create socket");
 		exit(1);
@@ -345,7 +357,19 @@
 	setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &curstate, sizeof(curstate));
 	/* the return value is ignored.. */
 
-	if (bind(sockfd, (struct sockaddr *)&addr, sizeof(addr)) < 0)  {
+	/*    Force dual stack    */
+	setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY, &ipv6only, sizeof(ipv6only));
+	/* the return value is ignored.. */
+
+	/*    Nagle and quickack  */
+	if ((setsockopt(sockfd, IPPROTO_TCP, TCP_NODELAY, &nodelay, sizeof(nodelay))) < 0) {
+		perror("Error setsockopt tcp_nodelay");
+	}
+	if ((setsockopt(sockfd, IPPROTO_TCP, TCP_QUICKACK, &quickack, sizeof(quickack))) < 0) {
+		perror("Error setsockopt tcp_quickack");
+	}
+
+	if (bind(sockfd, (struct sockaddr *) &addr, sizeof(addr)) < 0)  {
 		perror("can't bind");
 		exit(1);
 	}
@@ -365,7 +389,7 @@
  */
 static void start_connection(void)
 {
-	struct sockaddr_in addr;
+	struct sockaddr_in6 addr;
 	int i;
 	socklen_t addr_len;
 
@@ -394,30 +418,58 @@
  */
 static void init_client(char *server, int port)
 {
-	struct sockaddr_in addr;
-	struct hostent *host;
-	int curstate = 1;
-	int fd;
+	/*
+	*	RvdP, changed to support IPv6
+	*/
 
-	if ((fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0){
-		perror("create socket");
+	struct addrinfo hints;
+	struct addrinfo *result, *rp;
+	int curstate = 1;
+	int nodelay  = 1;
+	int quickack = 1;
+	int fd, s;
+	char portstr[8];
+
+	memset(&hints, 0, sizeof(struct addrinfo));
+	hints.ai_family   = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	/* hints.ai_protocol = IPPROTO_TCP; */
+	hints.ai_flags    = 0;
+
+	memset(portstr, 0, 8);
+	snprintf(portstr, 6, "%d", port);
+
+	s = getaddrinfo(server, portstr, &hints, &result);
+	if (s != 0) {
+		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
+		exit(1);
+	}
+	for (rp = result; rp != NULL; rp = rp->ai_next) {
+		fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
+		if (fd == -1)
+			continue;
+		if (connect(fd, rp->ai_addr, rp->ai_addrlen) != -1)
+			break;
+		close(fd);
+	}
+	if (rp == NULL) {
+		fprintf(stderr, "Could not connect\n");
 		exit(1);
 	}
+
 	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &curstate, sizeof(curstate)) < 0) {
 		perror("setsockopt");
 		exit(1);
 	}
-	if ((host = gethostbyname(server)) == NULL){
-		fprintf(stderr, _("can't get address %s\n"), server);
-		exit(1);
+
+	/*  RvdP, nagle and quickack  */
+	if ((setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &nodelay, sizeof(nodelay))) < 0) {
+		perror("Error setsockopt tcp_nodelay");
 	}
-	addr.sin_port = htons(port);
-	addr.sin_family = AF_INET;
-	memcpy(&addr.sin_addr, host->h_addr, host->h_length);
-	if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
-		perror("connect");
-		exit(1);
+	if ((setsockopt(fd, IPPROTO_TCP, TCP_QUICKACK, &quickack, sizeof(quickack))) < 0) {
+		perror("Error setsockopt tcp_quickack");
 	}
+
 	if (verbose)
 		fprintf(stderr, _("ok.. connected\n"));
 	netfd[0] = fd;