TCP ZeroWindow / TCP Window Full Networking Origin: Network OSI layer 4 · Transport Last updated 5 Nov 2026

Networking: Wireshark: TCP ZeroWindow, TCP Window Full — the receiver can't keep up and tells the sender to stop

The receiving application isn't reading data fast enough, so its TCP buffer filled and the sender must pause.

Exact message you may see TCP ZeroWindowTCP Window FullTCP ZeroWindowProbeTCP Window Updatereceive window zero
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Seen on: Linux Networking

Meaning

ZeroWindow is flow control working, but it means the receiver (app, disk, CPU, slow client) is the bottleneck, not the network. Profile the receiver, increase buffers only if justified, and check slow consumers, GC pauses and disk I/O.

Common causes

  • Receiving app too slow or blocked
  • Small socket receive buffer
  • Slow disk or database behind the receiver
  • High CPU, GC pause or thread starvation
  • Slow mobile client downloading

⚡ Quick fix

  1. Find the stalled process: ss -tnmp and check Recv-Q
  2. Fix the slow consumer (I/O, CPU, GC)
  3. Tune rmem only after fixing the app

Detailed fix by platform

Linux

  1. ss -tnmp state established | awk "$2>0" # non-zero Recv-Q means the app isn't reading

How to diagnose

  1. Recv-Q — Growing?
  2. Receiver — CPU/disk bound?
  3. Window — Zero repeatedly?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Network. Errors that are often confused with or caused by this one (click to open):

Cannot assign requested address (EADDRNOTAVAIL) — Networking: connect: Cannot assign requested address — ephemeral port range exhausted by TIME_WAIT connections (Networking)Cannot assign request…Connections hang on large transfers (PMTU black hole) — Networking: SSH/HTTPS connects but hangs on large data — path MTU discovery black hole (Networking)Connections hang on l…High TCP retransmissions / packet loss — Networking: netstat -s: segments retransmitted / Wireshark: TCP Retransmission, TCP Dup ACK — packet loss on the path (Networking)High TCP retransmissi…Many sockets in CLOSE_WAIT — Networking: Thousands of sockets in CLOSE_WAIT — the application is not closing its side of the connection (Networking)Many sockets in CLOSE…Possible SYN flooding on port 80. Sending cookies. — Networking: TCP: request_sock_TCP: Possible SYN flooding on port 80. Sending cookies. Check SNMP counters. (Networking)Possible SYN flooding…times the listen queue of a socket overflowed — Networking: netstat -s: 1523 times the listen queue of a socket overflowed — accept queue full, connections dropped (Networking)times the listen queu…UDP RcvbufErrors / packet receive errors — Networking: netstat -su: packet receive errors, receive buffer errors — UDP datagrams dropped by a full socket buffer (Networking)UDP RcvbufErrors / pa…TCP ZeroW…

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