socklab v6 Laboratory of Internet sockets User Guide
Contents
1. lt nb gt number of bytes to read 100 by default 4 3 10 D send lt id gt lt msg gt oob dontroute loop Description writing a message in the previous established connection on a socket lt td gt This command differs from write only the options it offers Parameters lt msg gt message to send cf write Options oob option Out Of Band to send the message in mode urgent dontroute option Don t Route for the message can not cross a router in other words he can not go outside the network on which the machine is connected loop This option does not appear in the standard primitive send In the spec ifying socklab v6 sends the message until an error intervene or you press Ctrl C 4 3 11 V recv lt id gt lt nb gt oob peek Description reading a message in the previous established connection on a socket lt id gt This command differs from read only by the options it offers Parameter lt nb gt number of bytes to read Options oob option Out Of Band to read the message in mode urgent peek option Peek to read the data while in the receive buffer This option allows you reread the same data 4 3 12 T sendto lt id gt lt host gt lt port gt lt mesg gt oob dontroute loop Description Sending a message to a specific destination socket The socket lt td gt is used as the source of the message UDP socket only Parameters lt host gt IPv6 a2. and bind 0 in standard mode 4 5 2 K close lt td gt Description same as close in standard mode 4 5 3 T sendto lt id gt lt host gt lt port gt lt msg gt Description same as sendto in standard mode fewer options 4 5 4 F recvfrom lt td gt lt nb gt Description same as recvfrom in standard mode fewer options 4 5 5 O0 options lt td gt lt options gt Description same as options in standard mode Index accept 11 14 17 bind 9 14 close 14 18 19 connect 14 17 exit 13 help 11 13 listen 14 options 17 19 passive 17 quit 13 read 15 17 18 recv 16 recvfrom 10 16 19 send 15 sendto 10 16 19 shutdown 15 18 socket 13 19 status 9 13 urecv 18 usend 18 write 15 18 20
3. directly related to the manipulation of sockets for ex ample displaying the state of sockets created displaying the list of available com mands 2 2 Operating Modes of socklab v6 socklab v6 can be used in three different operation modes Choosing one of these three modes determines the list of commands and control operations available for using socklab v6 in all three cases the list of special commands is invariant e In standard mode default mode a command is associated with each system allow to manipulate sockets ex primitives such as socket bind send By running a list of commands you can see the results you will get if you run a program in C which is linked with list of primitive equivalent e In TCP mode the range of available commands is directed to exclusive sockets TCP Primitives unrelated with TCP are not represented the commands available are less numerous than in standard mode Moreover the new commands are introduced to simplify the using of socklab v6 those commands have concatenation of several features e Similarly in UDP mode the list of available commands is directed to exclusive sockets with UDP Standard mode is normally used to study the primitive programming interface sockets how they work and discover their limits While TCP and UDP modes are normally used to study the respective protocols in service or in operation but in the last case the joint use of a traffic analyzer like snoop
4. ands can be given for short Moreover when a command has parameters ex the type of protocol for the command socket they can be directly entered on the line Thus to create a new TCP socket you can ask for different ways socket tcp sock tcp s tcpors t commands are equivalent As the parameter is passed directly on the line socklab v6 makes you a prompt when it has executed the primitive socket socklabv6 gt sock udp La socket est identifiee par 1 identificateur 4 socklabv6 gt Since the beginning of this demonstration two sockets have been created To check run the status command socklabv6 gt status Id Proto Adresse Connexion RWX 3 UDP W gt 4 UDP W socklabv6 gt This command displays all the information attached to sockets that have been created shortened form of the command status is For each socket displayed Id is identified Proto is the type of protocol used Adresse is the address which was possibly affected in the example above this is not the case Connexion indicates whether a connection is established and RWX indicates that it is possible to make R read W write X eXception cf 4 2 3 Note the sign gt to the left of the second socket This indicates what is the socket recently been created or manipulated You will now use the bind command which uses the primitive of the same name to assign an address to a socket In the Internet domain a socket is identified by an Internet addre
5. arameter you can specify a point to indicate that you want to use the latest socket created or manipulated 4 3 1 S socket tcpludp Description creating a socket in the Internet domaine type STREAM or DATAGRAM depending on the value of the parameter Parameter tcp creating a socket of type STREAM using TCP udp creating a socket of type DATAGRAM using UDP 4 3 2 B bind lt td gt lt host gt lt port gt Description assigning an address to the socket lt id gt Parameters lt host gt IPv6 Internet address assigned to the socket If the machine you re working on is connected to multiple networks it has several addresses This setting allows you to specify one You can type directly IPv6 address dot notation XXXX XXXX XXXX XXXX XXXX XXXX XXXX XXXX or you can give a symbolic name in the file etc hosts is a shorthand for the official name of the machine where you work You can specify the particular address in6addr_any with asterisk Address in6addr_any is generally used for passive TCP sockets in order to receive connection requests on any machine address lt port gt port number of the socket You can directly type the port number or you can give the name of a service in the file etc services By providing the value 0 the system automatically selects an available port number 4 3 3 L listen lt td gt lt nb gt Description listening setting of the socket lt td gt only TCP socket Param
6. ddress of the destination machine lt port gt number of the socket on the destination machine Options oob option Out Of Band cf send dontroute option Don t Route cf send loop option Loop cf send 4 3 13 F recvfrom lt td gt lt nb gt oob peek Description receiving on the socket lt td gt a message sent by a remote socket UDP socket only Parameter lt nb gt number of bytes to read Options oob option Out of Band cf recv peek option Peek cf recv 4 3 14 0 options lt td gt lt option gt Description viewing and editing options of the socket lt d gt Used without parameters this command reviews all options for the socket they are displayed one by one with their current value If you specify one or more specific options for each parameter the command only deals with them For not changing the value of an option type directly on Enter The next option is displayed The majority of options are boolean you must respond by o or n to modify them The option asynchrone allows to be notified when a message or a connection request arrives on the socket The option nodelay allows you to make non blocking primitives by default a read is blocked when no message is ready All other options are those that can be accessed or modified by the primitive getsockopt and setsockopt However all the options normally available are not shown in socklab v6 4 4 Command
7. dl de tr tr de Ded Ree ahh SY te PRs aah Y AAA ELOS 25d cag tele E ates Soh ee BO hee RE hee ee et aat NINDMD OD 00 4 5 ACA Shutdown 2 a A cE ah eS 18 AAG SMA te a A A A SSSA a ee 18 AAT o A RR RT 18 AAS E IE O a e aa 18 A OS UCV a e o Be Se che bok A tr Ge a8 os Gl 18 AAA o e O A A a A AA 18 Commands in UDP mode a 19 Al SOC KE ta loe Oe ER et ee aed keg Stns Me eg Sos 19 Adis ELOSSA 2 tA sede Ade ode Be hfe bak dS ee bs en an Oe OY en OE 19 ADOS SOLO t Sez A wh Get A Oa ee ee ee 19 ALA POCO a Bon lao Ron volando aa And Qe tans C 19 A OPERONS ete er ee Dees Oe gc Wn a ake ee aa ake A ain 19 Chapter 1 Introduction Within a same machine processes have some ways to connect between them files pipes signals messages but these processes must be executed on the same machine Two processes execute in two different machines can only communicate each other if these machines are connected But they have to use a programming interface it is a set of primitives whose purpose is to relate the processes in two machines There are many network programming interfaces in UNIX systems the most currently used is sockets BSD Berkeley Software Distribution First the socket term is used to designate access points that processes must handle to send or receive data By extension this term refers to any programming interface known as sockets Using this API is not easy it is rare that two processes even loca
8. er the mode of operation of the laboratory 12 4 2 1 QIX quitlexit Description These two commands are equivalent they can leave the lab to return to the shell Confirmation is still required all sockets created will be deleted upon termination of socklab v6 4 2 2 7 help lt cmd gt Description without parameters this command displays a list of all available com mands with the letter which can be used as a shortcut If command names are passed as a parameter the command displays only their syntax Parameter lt cmd gt Name of a command whose syntax must be displayed 4 2 3 status Description Displaying the status of all sockets created The last socket created or manipulated is indicated by the mark gt at the beginning of the line that describes it For each socket command displays 1 identifier 2 protocol used TCP or UDP 3 local address if it has one with its port number 4 address of the remote socket if a connection was made 5 feasible operations R read reading data or recovery a connexion W write writing data X exception reading exception 4 3 Standard Mode Commands In this mode all commands correspond to a particular primitive programming interface sockets the mode of operation of the laboratory by default The name of each command is one of the primitive manipulated In socket all commands have first identifier parameter lt id gt to which they apply For this p
9. eter lt nb gt number of connections can be maintained until the last ones are recovered by the command accept default nb 5 4 34 A accept lt id gt Description awaiting or recovery a connection on the socket lt td gt only TCP socket 4 3 5 C connect lt td gt lt host gt lt port gt Description connection socket lt td gt on a remote socket If the connection has been established a new socket will be created Parameters lt host gt name or IPv6 address of the remote machine cf bind lt port gt port number or service name on the remote machine 4 3 6 K close lt td gt Description closing the socket lt td gt 4 3 7 H shutdown lt id gt in out both Description closing the previous established connection on a socket lt 7d gt Parameter in closing input only out closing output only both closing in both directions 4 3 8 W write lt td gt lt msg gt Description writing a message in the previous established connection on a socket lt td gt Parameter lt msg gt message to send If you want to send several words you must limit them in quotes To send a specific number of bytes regardless of message content use the notation nnn where nnn is the number of bytes to send the message is composed by asterisks 4 3 9 R read lt td gt lt nb gt Description reading a message in the previous established connection on a socket lt td gt Parameter
10. ill display the port number chosen by the system To illustrate these last two points name the second UDP socket socklab v6 gt bind 4 O Le port 1043 a ete affecte a la socket socklabv6 gt Id Proto Adresse Connexion RWX 3 UDP sparc1 5000 z W gt 4 UDP 1043 W socklab v6 gt You may notice that the two sockets now have an address Until now you have used only two control commands socket and bind and a special command status For finishing you ll exchange a message between two UDP sockets created The primitive for sending a message using the UDP protocol called sendto The sendto command parameters are in order the identifier of the socket to use the machine destination the destination port number on that machine and message to send If the message consists several words you must use quotation marks if not all words will be considered as additional parameters Using sendto command send a message from the first socket created Id 3 to the second sparc1 port 1043 socklabv6 gt sendto 3 sparc1 1043 Voici un message 16 octet s envoye s socklabv6 gt On the second UDP socket marked with 4 in the example ask the reception of 20 bytes per command recvfrom This command has two parameters the number of the socket on which the message must be read and the number of bytes to read socklab v6 gt recvfrom 4 20 Un message de 16 octet s a ete recu de sparci 5000 Message lt Voici un message gt
11. ly Once the lab started you can access to a shell that lets you create select delete or manipulate sockets The laboratory maintains a permanent table which stored the list of sockets that you have created Most commands require one or more parameters You can specify as arguments on the command line otherwise they will be automatically applied when executing the command Some commands also have options such as the commands send or recv these options can be specified on the command line If you omit them they will not be required when running the command options are words that always start with a dash You can write the shorten names of commands parameters or options provided that the interpreter can identify them without ambiguity For example you can type so in stead of the socket command In contrast you can not type se instead of send command because the sendto commence also by se However each command is associated with a single letter which can be used in place of the full name At any time you can interrupt the progress of a command by pressing Ctrl C you will return automatically to the shell of the laboratory We will now describe separately all commands supported by the interpreter socklab v6 For each we show the first letter can be used as a shortcut then its possible parameters and options 4 2 Special commands Special orders are those that do not apply to a particular socket They are always available whatev
12. ng the laboratory in this mode without running socklab v6 option sparc1 socklabv6 socklab v6 laboratoire d etude des sockets INTERNET A BOUKIOUD amp Q DUONG R NASRI ENSIMAG Juin 2011 socklabv6 gt In this mode each primitive programming interface sockets has an associated com mand Therefore all commands have the same name as the primitive that they handle For example to create a socket call the system s socket Ask the execution of the command socket socklabv6 gt socket Protocole tcp udp The original socket normally has three parameters the area where the new socket must be created its type and protocol is used in the given type The laboratory is only used to study the Internet domain sockets Both types are only represented STREAM or DATAGRAM and each correspond a single protocol TCP or UDP respectively There fore socklab v6 just asks the protocol you want to use with the new socket Selecting UDP socklab v6 then has all the information necessary to call the original socket If the call does not fail socklab v6 returns the identifier of the socket that it has just created this is the descriptor number as the original socket returns Through this identifier you can now manipulate the socket socklab v6 gt socket Protocole tcp udp udp La socket est identifiee par 1 identificateur 3 socklab v6 gt In order not to make use of socklab v6 too cumbersome the names of comm
13. s in TCP mode TCP mode is the mode obtained by running the lab with the parameter tcp The objective of this mode is to study the TCP protocol and not the sockets themselves The available commands are less numerous but simple to use because they generally carry the sequence of several primitives manipulating sockets In passive and connect all the commands have first identifier parameter lt td gt of the socket to which they apply For this parameter you can specify a point to indicate that you want to use the latest socket created or manipulated 4 4 1 P passive Description creating a socket passive ready to receive connection requests The ad dress in6addr_any is automatically assigned and a free port number is chosen by the system equivalent to socket tcp bind Oandlisten 5 in standard mode 4 4 2 A accept lt td gt Description same as accept in standard mode 4 4 3 C connect lt host gt lt port gt Description creating an active socket and then attempt to connect to a remote socket The address in6addr_any is automatically assigned and a free port number is cho sen by the system equivalent to socket tcp bind 0 connect lt host gt lt port gt in standard mode Parameter lt host gt name or IPv6 address of the remote machine lt port gt port number of the socket on the remote machine 4 4 4 K close lt td gt Description same as close in standard mode 4 4 5 H shu
14. socklab v6 Laboratory of Internet sockets User Guide Reference Guide Amine BOUKIOUD Quang Ngoc DUONG Rafik NASRI Date 2011 06 06 Monday june 6th 2011 Contents Introduction General presentation 2 1 Classification of commands ci a Ble ra Soe e y 2 2 Operating Modes of sock lab v6 ig lt n oe a ace ho ee he ee oo a es a USe s amp ma Anh aS he Ae A ae ee le AR ee ES 2 4 Launch socklab MO ej a eS ee eh de edb ge es a ES Example of using socklab v6 socklab v6 s Reference Guide A PU TIAZ AO Lo E Ge ohare te Gey A A ee tes ME a e 4 2 Special commands ios E A A a a AL AUDE ee tr ts a A ici a A AOS 108 cs se he de ee 2s RN ADS Status oc amp hide tS Gee iets le That a dun Beadle ir lios 4 3 Standard Mode Commands i i a Ae eee EA eed hs ald G 4al ESOC KOE A a adh a Rake eg O he Shy Ad De Winds n dla rc e tudo tea a gh a ot od A AvS 3 A Ao accepte a hy eel E Ee Bee eon ete hs Sed ASD CONNEC Ha od A ee a ee ALSO ETORRI AST Shutdown aaa ah tera a le ets Bieta EN hee E ASSO e A te he Sa dn ew eee he ve ose be oe ee ee Pas AES 9S reade e who to A A ee Od a an SI Bock td a a hw A en eel Be wea Bp a eee ew A ASA A a a Ao sendt Osei tm dr Sag ta a A A A te ey Dada ALS LOEV TOM o di A lig Dhak tl eo eo lira A OPE VOUS sl E E Ce eRe E Seog 4 4 Commands in TCP mode 0 00000 ee en A Ad passive ds a Se watts woe wae kc eek ae AMD ACCEDE SADA Bhs Po Bl Bb ta tS ee a Boke Bef AAS CONNECT Bed
15. socklab v6 gt Now what happens when socklab v6 has a problem while running a command You try using the accept command on the last UDP socket created This command is reserved for the TCP protocol to retrieve a connection request on a socket passive It makes no sense for UDP socklab v6 gt accept 4 accept Operation not supported on transport endpoint socklab v6 gt When calling a primitive result in a failure a message describing the name of the primitive called and the error found is still displayed in reverse video this message is accompanied by a beep Note that using socklab v6 was shown on a single machine but you can obviously use the lab on two different machines connected by networks and implement communications between these two laboratories through socket TCP or UDP At any time you can request a list of available commands type help or socklabv6 gt help LISTE DES COMMANDES DISPONIBLES s socket r read w write help b bind v recv d send status 1 listen f recvfrom t sendto q quit a accept x exit c connect lt id gt select sock k close h shutdown o options socklabv6 gt Each command appears with a letter that might be used in its place as minimum abbreviation Chapter 4 socklab v6 s Reference Guide 4 1 Utilization The laboratory of sockets study starts by typing socklab v6 from a shell Specifying parameter udp or tcp you can guide the manipulation of sockets to UDP or TCP re spective
16. ss and a port number Running the bind command without arguments socklab v6 will ask you to enter the parameters one by one ie the identifier of the socket address internet address and port number to assign For some arguments socklab v6 offers default values as in the case of socket identifier by default socklab v6 offers the identifier of the last socket created or manipulated the one that appears with the gt sign with the status command If socklab v6 offers default values for arguments they appear in parentheses Just then press Enter to confirm In this example we assign to the socket identifier 3 the station address sparc1 replace with the address or name of the station where you work As for the port number we choose arbitrarily the number 5000 socklabv6 gt bind Id socket 4 3 Host sparcl Port 5000 socklabv6 gt When a station is connected to several networks it has several Internet addresses The primitive bind may accept a special website in6addr_any noted which means any address of the machine this is actually a generic address The notation for use with the bind command to designate that particular address is the asterisk Regarding to the port you can leave the operating system choosing a free port number if the previous operation in the port 5000 was already used the original bind would have omited To do this specify the port number 0 after running the initial bind socklab v6 w
17. tcpdump or ethereal is however necessary 2 3 Principle of use Whatever the mode of operation used the purpose of socklab v6 is to provide an in terface to create operate and remove sockets During one session with socklab v6 you can handle multiple sockets simultaneously This means that between each command socklab v6 maintains a list of sockets that you have created At any time you can select any previously created socket and use it to send or receive data through the appropriate commands 2 4 Launch socklab v6 socklab v6 normally appears in the directory usr local bin of stations Normally this directory is automatically included in the PATH environment variable Once launched socklab v6 displays a banner presentation followed by the prompt of the shell sparcl socklabv6 socklab v6 laboratoire d etude des sockets INTERNET A BOUKIOUD amp Q DUONG amp R NASRI ENSIMAG Juin 2011 socklab gt By default socklab v6 operates in standard mode To use UDP or TCP mode you must specify the option respectively udp or tcp on the command line The prompt socklab v6 is then modified to indicate the mode used For exemple sparcl socklabv6 tcp socklab v6 laboratoire d etude des sockets INTERNET A BOUKIOUD amp Q DUONG amp R NASRI ENSIMAG Juin 2011 socklabv6 TCP gt Chapter 3 Example of using socklab v6 In this section we will illustrate the use of socklab v6 in standard mode Starting by launchi
18. tdown lt id gt in out both Description same as shutdown in standard mode 4 4 6 W write lt td gt lt msg gt Description same as write in standard mode 4 4 7 R read lt d gt lt nb gt Description same as read in standard mode 4 4 8 D usend lt id gt lt msg gt Description Writing an urgent message to the previous established connection on a socket lt d gt equivalent to send lt td gt lt msg gt oob in standard mode Parameter lt msg gt message to send cf write 4 4 9 V urecv lt td gt lt nb gt Description reading an urgent message to the previous established connection on a socket lt id gt equivalent to recv lt nb gt oob in standard mode Parameter lt nb gt number of bytes to read 4 4 10 0 options lt td gt lt option gt Description same as options in standard mode 4 5 Commands in UDP mode UDP mode is the mode obtained by running the lab with the parameter udp The objective of this mode is to study the UDP protocol not the sockets themselves Apart from socket all the commands have first identifier parameter lt id gt to which they apply For this parameter you can specify a point to indicate that you want to use the latest socket created or manipulated 4 5 1 S socket Description Creating a UDP socket The address in6addr_any is automatically as signed and a free port number is chosen by the system equivalent to socket udp
19. ted on the same machine arrive at the first attempt to communicate via sockets Indeed the primitives are generally not used or misused data structures so that the first attempt is frequently unsuccessful not mention the errors that occur directly when compiling programs socklab v6 is a utility that allows you to manipulate sockets without having to compile a single line of code This laboratory study of sockets is in the form of shell where each command is associated with the call of a primitive interface sometimes many primitives Whenever you enter a command socklab v6 runs the corresponding original and gives you an account of this execution If you discover sockets socklab v6 will help you understand the role of different primitives and how they should be used what can be done what is forbidden If you have already known the sockets working with socklab v6 may be very useful to study their function or their limitations in some specific situations Version 4 of socklab was already available to manipulate IPv4 sockets In the version 6 you will manipulate with IPv6 sockets Chapter 2 General presentation 2 1 Classification of commands The commands of socklab v6 are classified into three categories 1 The control commands allow creating deleting or modifying their operation mode manipulation options 2 The operating commands allow sending or receiving messages through the socket 3 The special commands not
Download Pdf Manuals
Related Search