Echo protocol
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| The five-layer TCP/IP model |
|---|
| 5. Application layer |
|
DHCP · DNS · FTP · Gopher · HTTP · IMAP4 · IRC · NNTP · XMPP · POP3 · RTP · SIP · SMTP · SNMP · SSH · TELNET · RPC · RTCP · RTSP · TLS (and SSL) · SDP · SOAP · GTP · STUN · NTP · (more) |
| 4. Transport layer |
| TCP · UDP · DCCP · SCTP · RSVP · ECN · (more) |
| 3. Network/internet layer |
| IP (IPv4 · IPv6) · OSPF · IS-IS · BGP · IPsec · ARP · RARP · RIP · ICMP · ICMPv6 · IGMP · (more) |
| 2. Data link layer |
| 802.11 (WLAN) · 802.16 · Wi-Fi · WiMAX · ATM · DTM · Token ring · Ethernet · FDDI · Frame Relay · GPRS · EVDO · HSPA · HDLC · PPP · PPTP · L2TP · ISDN · ARCnet · LLTD · (more) |
| 1. Physical layer |
| Ethernet physical layer · RS-232 · SONET/SDH · G.709 · Optical fiber · Coaxial cable · Twisted pair · (more) |
The Echo service is an internet protocol defined in RFC 862. It was originally proposed as a way to test and measure an IP network. Now, testing and measurement is more commonly done with ping and traceroute.
A host may connect to a server that supports the Echo protocol on either TCP or UDP port 7. The server then sends back any data it receives, with no modification by the Echo server.
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[edit] Inetd implementation of Echo
On Linux, FreeBSD, and other UNIX-like operating systems an Echo server is built into the inetd daemon. The Echo service is usually not enabled by default. It may be enabled by adding the following lines to the file /etc/inetd.conf and telling inetd to reload its configuration:
echo stream tcp nowait root internal echo dgram udp wait root internal
[edit] Examples of use
- As a generic network service which is guaranteed to read, and additionally write back, what is sent to it. Such a service is useful for debugging TCP and UDP based network code (such as event-loops) without disrupting the current operation of existing services.
