README
¶
Package telnet
The telnet package provides basic
telnet client and server implementations for Go, including handling of IACs and
extensible telnet option negotiation.
Currently both the basic client and server are implemented, as well as a NAWS client/server handler as a working example. Additional handlers may be added to the core library over time (feel free to submit a PR if you've written one you'd like to see added!)
Usage
Running a server:
svr := telnet.NewServer(":9999", telnet.HandleFunc(func(c *telnet.Connection){
log.Printf("Connection received: %s", c.RemoteAddr())
c.Write([]byte("Hello world!\r\n"))
c.Close()
}))
svr.ListenAndServe()
The server API is modeled after the net/http API, so it should be easy to get
your bearings; of course, telnet and HTTP are very different beasts, so the
similarities are somewhat limited. The server listens on a TCP address for new
connections. Whenever a new connection is received, the connection handler is
called with the connection object. This object is a wrapper for the underlying
TCP connection, which aims to transparently handle IAC. There is a slightly
more complex example located in the example package.
Running a client is pretty simple:
conn, err := telnet.Dial("127.0.0.1:9999")
This is really straightforward - dial out, get a telnet connection handler back. Again, this handles IAC transparently, and like the Server, can take a list of optional IAC handlers. Bear in mind that some handlers - for example, the included NAWS handler - use different Option functions to register them with a client versus a server; this is because they may behave differently at each end. See the documentation for the options for more details.
Linereader
A sub-package, linereader, exposes a simple reader intended to be run in a
Goroutine, which consumes lines from an io.Reader and sends them over a
channel for asynchronous handling.
Documentation
¶
Overview ¶
The telnet package provides basic telnet client and server implementations. It includes handling of IACs and extensible telnet option negotiation for both clients and servers.
Running a server:
svr := telnet.NewServer(":9999", telnet.HandleFunc(func(c *telnet.Connection){
log.Printf("Connection received: %s", c.RemoteAddr())
c.Write([]byte("Hello world!\r\n"))
c.Close()
}))
svr.ListenAndServe()
The server API is modeled after the net/http API, so it should be easy to get your bearings; of course, telnet and HTTP are very different beasts, so the similarities are somewhat limited. The server listens on a TCP address for new connections. Whenever a new connection is received, the connection handler is called with the connection object. This object is a wrapper for the underlying TCP connection, which aims to transparently handle IAC.
Running a client is pretty simple:
conn, err := telnet.Dial("127.0.0.1:9999")
This is really straightforward - dial out, get a telnet connection handler back. Again, this handles IAC transparently, and like the Server, can take a list of optional IAC handlers. Bear in mind that some handlers - for example, the included NAWS handler - use different Option functions to register them with a client versus a server; this is because they may behave differently at each end. See the documentation for the options for more details.
Index ¶
Constants ¶
const ( TeloptBINARY = byte(0) // 8-bit data path TeloptECHO = byte(1) // echo TeloptRCP = byte(2) // prepare to reconnect TeloptSGA = byte(3) // suppress go ahead TeloptNAMS = byte(4) // approximate message size TeloptSTATUS = byte(5) // give status TeloptTM = byte(6) // timing mark TeloptRCTE = byte(7) // remote controlled transmission and echo TeloptNAOL = byte(8) // negotiate about output line width TeloptNAOP = byte(9) // negotiate about output page size TeloptNAOCRD = byte(10) // negotiate about CR disposition TeloptNAOHTS = byte(11) // negotiate about horizontal tabstops TeloptNAOHTD = byte(12) // negotiate about horizontal tab disposition TeloptNAOFFD = byte(13) // negotiate about formfeed disposition TeloptNAOVTS = byte(14) // negotiate about vertical tab stops TeloptNAOVTD = byte(15) // negotiate about vertical tab disposition TeloptNAOLFD = byte(16) // negotiate about output LF disposition TeloptXASCII = byte(17) // extended ascii character set TeloptLOGOUT = byte(18) // force logout TeloptBM = byte(19) // byte macro TeloptDET = byte(20) // data entry terminal TeloptSUPDUP = byte(21) // supdup protocol TeloptSUPDUPOUTPUT = byte(22) // supdup output TeloptSNDLOC = byte(23) // send location TeloptTTYPE = byte(24) // terminal type TeloptEOR = byte(25) // end or record TeloptTUID = byte(26) // TACACS user identification TeloptOUTMRK = byte(27) // output marking TeloptTTYLOC = byte(28) // terminal location number Telopt3270REGIME = byte(29) // 3270 regime TeloptX3PAD = byte(30) // X.3 PAD TeloptNAWS = byte(31) // window size TeloptTSPEED = byte(32) // terminal speed TeloptLFLOW = byte(33) // remote flow control TeloptLINEMODE = byte(34) // Linemode option TeloptXDISPLOC = byte(35) // X Display Location TeloptOLDENVIRON = byte(36) // Old - Environment variables TeloptAUTHENTICATION = byte(37) // Authenticate TeloptENCRYPT = byte(38) // Encryption option TeloptNEWENVIRON = byte(39) // New - Environment variables TeloptEXOPL = byte(255) // extended-options-list )
Telnet Options
const ( TelQualIS = byte(0) // option is... TelQualSEND = byte(1) // send option TelQualINFO = byte(2) // ENVIRON: informational version of IS TelQualREPLY = byte(2) // AUTHENTICATION: client version of IS TelQualNAME = byte(3) // AUTHENTICATION: client version of IS LFlowOFF = byte(0) // Disable remote flow control LFlowON = byte(1) // Enable remote flow control LFlowRESTARTANY = byte(2) // Restart output on any char LFlowRESTARTXON = byte(3) // Restart output only on XON )
sub-option qualifiers
const ( EncryptIS = byte(0) // I pick encryption type ... EncryptSUPPORT = byte(1) // I support encryption types ... EncryptREPLY = byte(2) // Initial setup response EncryptSTART = byte(3) // Am starting to send encrypted EncryptEND = byte(4) // Am ending encrypted EncryptREQSTART = byte(5) // Request you start encrypting EncryptREQEND = byte(6) // Request you send encrypting EncryptENCKEYID = byte(7) EncryptDECKEYID = byte(8) EncryptCNT = byte(9) EncTypeANY = byte(0) EncTypeDESCFB64 = byte(1) EncTypeDESOFB64 = byte(2) EncTypeCNT = byte(3) )
ENCRYPTion suboptions
const ( SUSP = byte(237) ABORT = byte(238) EOR = byte(239) SE = byte(240) NOP = byte(241) DM = byte(242) BRK = byte(243) IP = byte(244) AO = byte(245) AYT = byte(246) EC = byte(247) EL = byte(248) GA = byte(249) SB = byte(250) WILL = byte(251) WONT = byte(252) DO = byte(253) DONT = byte(254) IAC = byte(255) )
Telnet IAC constants
const Escape = byte('\033')
Variables ¶
var ( // styles Reset = []byte("\033[0m") Bold = []byte("\033[1m") Underline = []byte("\033[4m") Conceal = []byte("\033[8m") NormalWeight = []byte("\033[22m") NoUnderline = []byte("\033[24m") Reveal = []byte("\033[28m") // colors - foreground FGBlack = []byte("\033[30m") FGRed = []byte("\033[31m") FGGreen = []byte("\033[32m") FGYellow = []byte("\033[33m") FGBlue = []byte("\033[34m") FGMagenta = []byte("\033[35m") FGCyan = []byte("\033[36m") FGWhite = []byte("\033[37m") FGDefault = []byte("\033[39m") // background BGBlack = []byte("\033[40m") BGRed = []byte("\033[41m") BGGreen = []byte("\033[42m") BGYellow = []byte("\033[43m") BGBlue = []byte("\033[44m") BGMagenta = []byte("\033[45m") BGCyan = []byte("\033[46m") BGWhite = []byte("\033[47m") BGDefault = []byte("\033[49m") // xterm TitleBarFmt = "\033]0;%s\a" )
ANSI control sequences
var EncTypeNames = []string{
"ANY", "DES_CFB64", "DES_OFB64"}
EncTypeNames is a mapping of bytes to strings for EncType constants.
var EncryptNames = []string{
"IS", "SUPPORT", "REPLY", "START", "END",
"REQUEST-START", "REQUEST-END", "ENC-KEYID", "DEC-KEYID"}
EncryptNames is a mapping of bytes to strings for Encrypt constants.
var TelOpts = []string{"BINARY", "ECHO", "RCP", "SUPPRESS GO AHEAD", "NAME",
"STATUS", "TIMING MARK", "RCTE", "NAOL", "NAOP",
"NAOCRD", "NAOHTS", "NAOHTD", "NAOFFD", "NAOVTS",
"NAOVTD", "NAOLFD", "EXTEND ASCII", "LOGOUT", "BYTE MACRO",
"DATA ENTRY TERMINAL", "SUPDUP", "SUPDUP OUTPUT",
"SEND LOCATION", "TERMINAL TYPE", "END OF RECORD",
"TACACS UID", "OUTPUT MARKING", "TTYLOC",
"3270 REGIME", "X.3 PAD", "NAWS", "TSPEED", "LFLOW",
"LINEMODE", "XDISPLOC", "OLD-ENVIRON", "AUTHENTICATION",
"ENCRYPT", "NEW-ENVIRON"}
TelOpts gives you a mapping of index to a textual representation of the telnet option.
Functions ¶
This section is empty.
Types ¶
type Connection ¶
type Connection struct {
// The underlying network connection.
net.Conn
// OptionHandlers handle IAC options; the key is the IAC option code.
OptionHandlers map[byte]Negotiator
// contains filtered or unexported fields
}
Connection to the telnet server. This lightweight TCPConn wrapper handles telnet control sequences transparently in reads and writes, and provides handling of supported options.
func Dial ¶
func Dial(addr string, options ...Option) (conn *Connection, err error)
Dial establishes a telnet connection with the remote host specified by addr in host:port format. Any specified option handlers will be applied to the connection if it is successful.
func NewConnection ¶
func NewConnection(c net.Conn, options []Option) *Connection
NewConnection initializes a new Connection for this given TCPConn. It will register all the given Option handlers and call Offer() on each, in order.
func (*Connection) RawWrite ¶
func (c *Connection) RawWrite(b []byte) (n int, err error)
RawWrite writes raw data to the connection, without escaping done by Write. Use of RawWrite over Conn.Write allows Connection to do any additional handling necessary, so long as it does not modify the raw data sent.
func (*Connection) Read ¶
func (c *Connection) Read(b []byte) (n int, err error)
Read from the connection, transparently removing and handling IAC control sequences. It may attempt multiple reads against the underlying connection if it receives back only IAC which gets stripped out of the stream.
func (*Connection) SetWindowTitle ¶
func (c *Connection) SetWindowTitle(title string)
SetWindowTitle attempts to set the client's telnet window title. Clients may or may not support this.
type HandleFunc ¶
type HandleFunc func(conn *Connection)
HandleFunc makes it easy to pass a function as a Handler instead of a full type.
func (HandleFunc) HandleTelnet ¶
func (f HandleFunc) HandleTelnet(conn *Connection)
HandleTelnet implements Handler, and simply calls the function.
type Handler ¶
type Handler interface {
HandleTelnet(conn *Connection)
}
Handler is a telnet connection handler. The Handler passed to a server will be called for all incoming connections.
type Negotiator ¶
type Negotiator interface {
// OptionCode returns the 1-byte option code that indicates this option.
OptionCode() byte
// Offer is called when a new connection is initiated. It offers the handler
// an opportunity to advertise or request an option.
Offer(conn *Connection)
// HandleDo is called when an IAC DO command is received for this option,
// indicating the client is requesting the option to be enabled.
HandleDo(conn *Connection)
// HandleWill is called when an IAC WILL command is received for this
// option, indicating the client is willing to enable this option.
HandleWill(conn *Connection)
// HandleSB is called when a subnegotiation command is received for this
// option. body contains the bytes between `IAC SB <OptionCode>` and `IAC
// SE`.
HandleSB(conn *Connection, body []byte)
}
Negotiator defines the requirements for a telnet option handler.
type Option ¶
type Option func(c *Connection) Negotiator
Option functions add handling of a telnet option to a Server. The Option function takes a connection (which it can store but needn't) and returns a Negotiator; it is up to the Option function whether a single instance of the Negotiator is reused or if a new instance is created for each connection.
type Server ¶
type Server struct {
// Address is the addres the Server listens on.
Address string
// contains filtered or unexported fields
}
Server listens for telnet connections.
func (*Server) ListenAndServe ¶
ListenAndServe runs the telnet server by creating a new Listener using the current Server.Address, and then calling Serve().
Source Files
Directories