diff -Naur asterisk-old/channels/chan_sip.c asterisk/channels/chan_sip.c
--- asterisk-old/channels/chan_sip.c	2004-07-16 12:26:24.394003037 -0500
+++ asterisk/channels/chan_sip.c	2004-07-16 12:39:56.301883800 -0500
@@ -3596,7 +3596,7 @@
 {
 	char iabuf[INET_ADDRSTRLEN];
 	/* Construct Contact: header */
-	if (ourport != 5060)
+	if ((ourport != 5060) && (ourport != 0))
 		snprintf(p->our_contact, sizeof(p->our_contact), "<sip:%s%s%s:%d>", p->exten, ast_strlen_zero(p->exten) ? "" : "@", ast_inet_ntoa(iabuf, sizeof(iabuf), p->ourip), ourport);
 	else
 		snprintf(p->our_contact, sizeof(p->our_contact), "<sip:%s%s%s>", p->exten, ast_strlen_zero(p->exten) ? "" : "@", ast_inet_ntoa(iabuf, sizeof(iabuf), p->ourip));
@@ -3635,18 +3635,18 @@
 	if (!ast_strlen_zero(p->fromuser))
 		l = p->fromuser;
 
-	if ((ourport != 5060) && ast_strlen_zero(p->fromdomain))
+	if ((ourport != 5060) && (ourport != 0) && ast_strlen_zero(p->fromdomain))
 		snprintf(from, sizeof(from), "\"%s\" <sip:%s@%s:%d>;tag=as%08x", n, l, ast_strlen_zero(p->fromdomain) ? ast_inet_ntoa(iabuf, sizeof(iabuf), p->ourip) : p->fromdomain, ourport, p->tag);
 	else
 		snprintf(from, sizeof(from), "\"%s\" <sip:%s@%s>;tag=as%08x", n, l, ast_strlen_zero(p->fromdomain) ? ast_inet_ntoa(iabuf, sizeof(iabuf), p->ourip) : p->fromdomain, p->tag);
 
 	if (!ast_strlen_zero(p->username)) {
-		if (ntohs(p->sa.sin_port) != DEFAULT_SIP_PORT) {
+		if (ntohs(p->sa.sin_port) != DEFAULT_SIP_PORT && ntohs(p->sa.sin_port) != 0) {
 			snprintf(invite, sizeof(invite), "sip:%s@%s:%d",p->username, p->tohost, ntohs(p->sa.sin_port));
 		} else {
 			snprintf(invite, sizeof(invite), "sip:%s@%s",p->username, p->tohost);
 		}
-	} else if (ntohs(p->sa.sin_port) != DEFAULT_SIP_PORT) {
+	} else if (ntohs(p->sa.sin_port) != DEFAULT_SIP_PORT && ntohs(p->sa.sin_port) != 0) {
 		snprintf(invite, sizeof(invite), "sip:%s:%d", p->tohost, ntohs(p->sa.sin_port));
 	} else {
 		snprintf(invite, sizeof(invite), "sip:%s", p->tohost);