TCP checks from Belgrade (AS51430) attempt a full SYN-ACK handshake to your host and measure connection time. This verifies port reachability from Serbian network infrastructure without ICMP filtering interference. AltusHost operates a commercial hosting network and does not filter outbound TCP connections on standard ports, making our Serbian TCP probes a clean test of what your firewall and routing present to Balkan-origin traffic.

Common use cases for TCP checks from Serbia: verifying game server ports for Balkan player bases, confirming mail server reachability (ports 25, 587, 465, 993) for Serbian email senders, testing VPN endpoint availability for regional deployments. Some hosting providers apply geo-fencing that blocks entire Balkan ASNs on specific ports — a TCP check from Belgrade will reveal this immediately while a ping check would not, since ICMP and TCP may take different firewall paths.

TCP handshake times from Belgrade: to Budapest approximately 18–22 ms, to Vienna approximately 28–34 ms, to Frankfurt approximately 44–52 ms. For services with SLA thresholds for Balkan users, these numbers define the minimum achievable connection setup latency. An application requiring sub-10 ms TCP handshake from Serbia needs an origin within the country or at a co-located Belgrade facility.

Belgrade is the largest network hub in the Western Balkans. SIX (Serbian Internet Exchange), hosted at Telehouse Belgrade, is the primary domestic peering point and a RIPE NCC member. It connects Serbian ISPs, regional carriers, and CDN providers, and its presence in Telehouse makes it co-located with a significant portion of Serbia's colocation market. Our probe node runs on AS51430 (AltusHost B.V.) in Belgrade, a provider with EU-wide hosting operations and strong regional BGP peering.

Serbia sits at a geographic crossroads between Central and Southeastern Europe, with good terrestrial transit connectivity in multiple directions. Belgrade-to-Budapest runs approximately 18–22 ms, Belgrade-to-Sofia approximately 13–17 ms, Belgrade-to-Vienna approximately 28–34 ms, and Belgrade-to-Zagreb approximately 10–14 ms. This central Balkan position means Serbian-hosted infrastructure is within low-latency reach of Hungary, Bulgaria, Romania, Croatia, and Bosnia simultaneously — making Belgrade a practical regional origin for Balkan-facing services.

The Serbian ISP market is anchored by Telekom Srbija (AS8400), which operates the national backbone and holds the largest fixed-line subscriber base. Serbia Broadband (SBB, AS31042) serves the commercial and cable market. Telenor Serbia and Yettel operate mobile and broadband networks. On the hosting and transit side, AltusHost (AS51430), Veesp, and several regional providers operate colocation in Belgrade. Transit upstream for Serbian networks typically routes through RETN (AS9002), Cogent (AS174), Level3/Lumen (AS3356), and Telekom Srbija's own international transit.

Belgrade's Telehouse data center is the primary carrier-neutral facility in Serbia and acts as the physical interconnect hub for most carrier peering in the country. SIX operates within Telehouse, giving colocation customers at that facility direct access to the IX fabric without additional cross-connects. Several international CDN providers, including Cloudflare and Akamai, have edge nodes in or around Belgrade, which measurably improves response times for Serbian users accessing major content platforms versus routing to Vienna or Frankfurt.

AltusHost (AS51430) has a broader EU footprint beyond Belgrade, with presence in the Netherlands and other markets, which means its BGP routing is more sophisticated than a purely local ISP. Results from our Belgrade node on AS51430 will reflect the routing decisions of a commercially-oriented hosting provider with multiple upstream transit providers rather than the residential or national-backbone routing that Telekom Srbija would show. For checks targeting international infrastructure, this is generally the more relevant probe for professional use cases.