Developing transport-independent applications using the Windows Sockets interface

The Windows Sockets Electronic Discussion List Page 1 of 50 'HYHORSLQJ7UDQVSRUW,QGHSHQGHQW$SSOLFDWLRQV 8VLQJWKH:...

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The Windows Sockets Electronic Discussion List

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struct sockaddr { u_short sa_family; char sa_data[14]; }; struct sockaddr_in { short sin_family; u_short sin_port; struct in_addr sin_addr; char sin_zero[8]; }; 7KHVRFNDGGUVWUXFWXUHLVXVHGE\:LQGRZV6RFNHWVWRVSHFLI\DORFDORUUHPRWHHQGSRLQWDGGUHVVWRZKLFKWRFRQQHFWDVRFNHW$QHQGSRLQW DGGUHVVVLPSO\FRQWDLQVWKHDSSURSULDWHLQIRUPDWLRQWRVHQGGDWDEHWZHHQWZRVRFNHWVRQGLIIHUHQWV\VWHPV$VWKHFRQWHQWVRIHQGSRLQW DGGUHVVHVGLIIHUEHWZHHQQHWZRUNSURWRFROIDPLOLHVWKHVRFNDGGUVWUXFWXUHZDVGHVLJQHGWRDFFRPPRGDWHHQGSRLQWDGGUHVVHVRIYDULDEOHVL]H VDWLVI\LQJUHTXLUHPHQWVRIPDQ\FRPPRQQHWZRUNSURWRFROIDPLOLHV7KHILUVWILHOGRIDVRFNDGGUFRQWDLQVWKHIDPLO\QXPEHULGHQWLI\LQJWKH IRUPDWRIWKHUHPDLQLQJSDUWRIWKHDGGUHVV ,QWKH,QWHUQHWDGGUHVVIDPLO\WKHVRFNDGGUBLQVWUXFWXUHLVXVHGWRVWRUHWKHHQGSRLQWDGGUHVVLQIRUPDWLRQDQGLVFDVWWRW\SHVRFNDGGUIRUWKH IXQFWLRQVZKLFKUHTXLUHLW2WKHUDGGUHVVIDPLOLHVPXVWGHILQHWKHLURZQVRFNDGGUBVWUXFWXUHVDVDSSURSULDWHIRUWKHLUQHHGV)RU7&3,3WKH VRFNDGGUBLQVWUXFWXUHEUHDNVWKHHQGSRLQWDGGUHVVLQWRLWVWZRFRPSRQHQWVSRUW,'VLQBSRUW DQG,3DGGUHVVVLQBDGGU DQGSDGVWKH UHPDLQLQJHLJKWE\WHVRIWKHHQGSRLQWDGGUHVVZLWKDFKDUDFWHUVWULQJVLQB]HUR 7KHSRUWDQG,3DGGUHVVYDOXHVDUHDOZD\VVSHFLILHGLQ QHWZRUNE\WHRUGHU7KHYDOXHIRUVLQBIDPLO\XQGHU7&3,3LVDOZD\V$)B,1(7DGGUHVVIDPLO\,QWHUQHW

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hostent { char FAR * char FAR * FAR * short short char FAR * FAR *

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h_name; h_aliases; h_addrtype; h_length; h_addr_list;

}; 7KHKRVWHQWVWUXFWXUHLVJHQHUDOO\XVHGE\WKH:LQGRZV6RFNHWVGDWDEDVHURXWLQHVWRUHWXUQKRVWRUV\VWHPLQIRUPDWLRQDERXWDVSHFLILHG V\VWHPRQWKHQHWZRUN7KHKRVWVWUXFWXUHFRQWDLQVWKHSULPDU\QDPHIRUDV\VWHPLQFOXGLQJRSWLRQDODOLDVHVIRUWKHSULPDU\QDPH $GGLWLRQDOO\LWFRQWDLQVDOLVWRIDGGUHVVHV IRUWKHVSHFLILHGV\VWHP7KLVLQIRUPDWLRQLVJHQHUDOO\VRXJKWIRUWKHUHPRWHV\VWHPWRZKLFKDQ DSSOLFDWLRQLVFRQQHFWLQJXVLQJWKH:LQGRZV6RFNHWVGDWDEDVHURXWLQHVGHVFULEHGODWHU

struct

protoent { char FAR * char FAR * FAR * short

p_name; p_aliases; p_proto;

servent { char FAR * char FAR * FAR * short char FAR *

s_name; s_aliases; s_port; s_proto;

}; struct

}; 7KHSURWRHQWDQGVHUYHQWVWUXFWXUHVDUHDOVRILOOHGE\WKH:LQGRZV6RFNHWVGDWDEDVHURXWLQHV7KHVHVWUXFWXUHVFRQWDLQLQIRUPDWLRQDERXWD SDUWLFXODUSURWRFRO7&3RU8'3 RUVHUYLFHILQJHURUWHOQHWIRUH[DPSOH UHVSHFWLYHO\$ORQJZLWKWKHSULPDU\QDPHDQGDQDUUD\RIDOLDVHV IRUWKHSURWRFRORUVHUYLFHWKHVHVWUXFWXUHVDOVRFRQWDLQWKHLUFRUUHVSRQGLQJELW,'VQHFHVVDU\WREXLOGDYDOLG7&3,3HQGSRLQWDGGUHVV

typedef struct WSAData { WORD WORD char char unsigned short unsigned short char FAR * } WSADATA;

wVersion; wHighVersion; szDescription[WSADESCRIPTION_LEN+1]; szSystemStatus[WSASYS_STATUS_LEN+1]; iMaxSockets; iMaxUdpDg; lpVendorInfo;

)LQDOO\WKH:6$'DWDVWUXFWXUHLVILOOHGLQE\D:LQGRZV6RFNHWV'//ZKHQDQDSSOLFDWLRQFDOOVWKH:6$6WDUWXS $3,$ORQJZLWK:LQGRZV

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6RFNHWVYHUVLRQLQIRUPDWLRQWKHVWUXFWXUHDOVRFRQWDLQVYHQGRUVSHFLILFLQIRUPDWLRQVXFKDVWKHPD[LPXPQXPEHURIVRFNHWVDYDLODEOHDQG WKHPD[LPXPGDWDJUDPVL]H7KHV]'HVFULSWLRQDQGV]6\VWHP6WDWXVPHPEHUVFDQEHXVHGE\DQLPSOHPHQWDWLRQWRLGHQWLI\LWVHOIDQGWKH FXUUHQWVWDWXVRIWKH'//)RUH[DPSOHDQLPSOHPHQWDWLRQPD\UHWXUQWKHWH[W-RH V6KDUH:DUH:LQGRZV6RFNHWVLPSOHPHQWDWLRQY LQV]'HVFULSWLRQ7KHVSHFLILFDWLRQRIWKHOS9HQGRU,QIRPHPEHULVFRPSOHWHO\XSWRDQLPSOHPHQWRUDQGLVQRWGHILQHGLQWKH :LQGRZV6RFNHWVVSHFLILFDWLRQ

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#define #define #define #define WSADATA char int

WS_VERSION_REQD WS_VERSION_MAJOR WS_VERSION_MINOR MIN_SOCKETS_REQD

0x0101 HIBYTE(WS_VERSION_REQD) LOBYTE(WS_VERSION_REQD) 6

wsaData; buf[MAX_BUF_LEN]; error;

. . . error=WSAStartup(WS_VERSION_REQUIRED,&wsaData); if (error !=0 ) { /* Report that Windows Sockets did not respond to the WSAStartup() call */

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sprintf(buf,"WINSOCK.DLL not responding."); MessageBox (hWnd, buf. "Windows Sockets Error",MB_OK); shutdown_app(); } if (( LOBYTE (wsaData.wVersion) < WS_VERSION_MAJOR) || ( LOBYTE (wsaData.wVersion) == WS_VERSION_MAJOR && HIBYTE (wsaData.wVersion) < WS_VERSION_MINOR)) { /* Report that the application requires Windows Sockets version WS_VERSION_REQD */ /* compliance and that the WINSOCK.DLL on the system does not support it. */ sprintf(buf,"Windows Sockets version %d.%d not supported by WINSOCK.DLL", LOBYTE (wsaData.wVersion), HIBYTE (wsaData.wVersion)); MessageBox (hWnd, buf. "Windows Sockets Error",MB_OK); shutdown_app(); } if (wsaData.iMaxSockets < MIN_SOCKETS_REQUIRED ) { /* Report that WINSOCK.DLL was unable to support the minimum number of */ /* sockets (MIN_SOCKETS_REQD) for the application */ sprintf(buf,"This application requires a minimum of %d supported sockets.", MIN_SOCKETS_REQUIRED); MessageBox (hWnd, buf. "Windows Sockets Error",MB_OK); shutdown_app(); } . $:LQGRZV6RFNHWVDSSOLFDWLRQJHQHUDOO\FDOOV:6$&OHDQXS GXULQJLWVRZQFOHDQXSGHFUHPHQWLQJWKHLQWHUQDOUHIHUHQFHFRXQWDQGOHWWLQJ :LQGRZV6RFNHWVNQRZWKDWLW VQRORQJHUQHHGHGE\WKHFDOOLQJDSSOLFDWLRQ:KDWHYHUFOHDQXSWKLVIXQFWLRQIRUFHVLVLPSOHPHQWDWLRQVSHFLILF DQGVKLHOGHGIURPWKHDSSOLFDWLRQ7KHDSSOLFDWLRQDXWKRUVKRXOGKRZHYHUFKHFNIRUDQ\SRVVLEOHHUURUFRQGLWLRQVIURP:6$&OHDQXS DQG UHSRUWWKHPEHIRUHH[LWLQJDVWKLVLQIRUPDWLRQPLJKWLQGLFDWHDQHWZRUNOD\HUSUREOHPLQWKHV\VWHP

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LPHOSTENT host_info; char user_buf[MAX_BUF], appl_buf[MAX_BUF]; . . . /* Attempt to resolve hostname specified by XVHUBEXIreturn meaningful */ /* message to the user in the event of an error. */ host_info=gethostbyname(user_buf); if(host_info==NULL){ sprintf(buf,"Windows Sockets error %d: Hostname: %s couldn’t be resolved.", WSAGetLastError(),user_buf); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK);} . . . ,QDGGLWLRQWRWKH:6$*HW/DVW(UURU $3,DQDSSOLFDWLRQPD\FKRRVHWRXVHWKH:6$6HW/DVW(UURU $3,WRVHWDQHWZRUNHUURUFRQGLWLRQZKLFK ZLOOEHUHWXUQHGE\DVXEVHTXHQW:6$*HW/DVW(UURU FDOO2EYLRXVO\DQ\:LQGRZV6RFNHWVFDOOVPDGHEHWZHHQD:6$6HW/DVW(UURU DQG :6$*HW/DVW(UURU SDLUZLOORYHUULGHWKHFRGHVHWE\WKH:6$6HW/DVW(UURU FDOO

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

char buf [MAX_BUF_LEN]; struct sockaddr_in srv_addr; LPSERVENT srv_info; LPHOSTENT host_info; SOCKET s; . . . /* Get FTP service port information */ srv_info=getservbyname("ftp","tcp"); if (srv_info== NULL) { /* Couldn’t find an entry for "ftp" over "tcp" */ sprintf(buf,"Windows Sockets error %d: Couldn’t resolve FTP service port.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Set up socket */ srv_addr.sin_family = AF_INET; srv_addr.sin_addr.s_addr = INADDR_ANY; srv_addr.sin_port=srv_info->s_port; 7KHH[DPSOHXVHVJHWVHUYE\QDPH WRUHVROYHWKHSRUWQXPEHURIWKH)73VHUYLFHRYHU7&37KHSRUW,'LVXVHGWRFRQVWUXFWWKHVRFNDGGUBLQ VWUXFWXUHHQGSRLQWDGGUHVV IRUIXWXUHXVHE\WKHDSSOLFDWLRQ$VZHPHQWLRQHGEHIRUHWKHDGGUHVVIDPLO\IRU7&3,3LVDOZD\VDVVLJQHGDV

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SOCKET cli_sock, srv_sock; LPSOCKADDR_IN cli_addr; char *cli_ip, buf[MAX_BUF]; int len; . /* Accept incoming connection, create new local socket cli_sock */ cli_sock=accept(srv_sock,(LPSOCKADDR)&cli_addr,&len); if (cli_sock==INVALID_SOCKET){ return(ERROR); } /* Convert endpoint IP address from network byte order to ASCII */ cli_ip=inet_ntoa(cli_addr.sin_addr); sprintf(buf,"Incoming connection request from: %s.\n",cli_ip); log_event(buf);

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#define

SERVICE_PORT

SOCKET

srv_sock,

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5001 cli_sock;

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The Windows Sockets Electronic Discussion List struct sockaddr_in srv_addr, char buf[MAX_BUF_LEN];

Page 19 of 50 cli_addr;

/* Create the server-side socket */ srv_sock=socket(AF_INET,SOCK_STREAM,0); if (srv_sock==INVALID_SOCKET){ sprintf(buf,"Windows Sockets error %d: Couldn’t create socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } srv_addr.sin_family=AF_INET; srv_addr.sin_addr.s_addr=INADDR_ANY; srv_addr.sin_port=SERVICE_PORT;

/* specific port for server to listen on */

/* Bind socket to the appropriate port and interface (INADDR_ANY) */ if (bind(srv_sock,(LPSOCKADDR)&srv_addr,sizeof(srv_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t bind socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Listen for incoming connections */ if (listen(srv_sock,1)==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t set up listen on socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Accept and service incoming connection requests indefinitely */ for ( ; ; ) { cli_sock=accept(srv_sock,(LPSOCKADDR)&cli_addr,&addr_len); if (cli_sock==INVALID SOCKET){ sprintf(buf,"Windows Sockets error %d: Couldn’t accept incoming \ connection on socket.",WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app();

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} . /* Client-server network interaction takes place here */ . closesocket(cli_sock); } &OLHQWVLGHFRQQHFWLRQRULHQWHG

/* Static IP address for remote server for example. In reality, this would be specified as a hostname or IP address by the user */ #define

SERVER

"131.107.1.121"

struct sockaddr_in srv_addr,cli_addr; LPSERVENT srv_info; LPHOSTENT host_info; SOCKET cli_sock; . /* Set up client socket */ cli_sock=socket(PF_INET,SOCK_STREAM,0); if (cli_sock==INVALID_SOCKET){ sprintf(buf,"Windows Sockets error %d: Couldn’t create socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } cli_addr.sin_family=AF_INET; cli_addr.sin_addr.s_addr=INADDR_ANY; cli_addr.sin_port=0; /* no specific port req’d */ /* Bind client socket to any local interface and port */ if (bind(cli_sock,(LPSOCKADDR)&cli_addr,sizeof(cli_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t bind socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); }

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/* Get the remote port ID to connect to for FTP service */ srv_info=getservbyname("ftp","tcp"); if (srv_info== NULL) { sprintf(buf,"Windows Sockets error %d: Couldn’t resolve FTP service port.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } srv_addr.sin_family = AF_INET; srv_addr.sin_addr.s_addr = inet_addr(SERVER); srv_addr.sin_port=srv_info->s_port; /* Connect to FTP server at address SERVER */ if (connect(cli_sock,(LPSOCKADDR)&srv_addr,sizeof(srv_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t connect socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Client-server network interaction takes place here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6HWWLQJXSDVHUYHUVLGHGDWDJUDPEDVHGDSSOLFDWLRQ

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6RPHVDPSOHFRGHLOOXVWUDWHVKRZWKH7)73SURWRFRODFRQQHFWLRQOHVVSURWRFROIRUILOHWUDQVIHU FOLHQWDQGVHUYHUPLJKWEHLPSOHPHQWHGRYHU :LQGRZV6RFNHWV

6HUYHUVLGHFRQQHFWLRQOHVV

SOCKET srv_sock; struct sockaddr_in srv_addr; . . /* Create server socket for connectionless service */ srv_sock=socket(PF_INET,SOCK_DGRAM,0); if (srv_sock==INVALID_SOCKET){ sprintf(buf,"Windows Sockets error %d: Couldn’t create socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Resolve TFTP service port to listen on */ srv_info=getservbyname("tftpd","udp"); if (srv_info== NULL) { sprintf(buf,"Windows Sockets error %d: Couldn’t resolve TFTPd service port.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } srv_addr.sin_family = AF_INET; srv_addr.sin_addr.s_addr = INADDR_ANY; srv_addr.sin_port=srv_info->s_port;

/* Allow the server to accept connections

/* over any inte

/* Bind remote server’s address and port */ if (bind(srv_sock,(LPSOCKADDR)&srv_addr,sizeof(srv_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t bind socket.", WSAGetLastError());

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MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Client-server network interaction takes place here */ &OLHQWVLGHFRQQHFWLRQOHVV

/* Static IP address for remote server for example. In reality, this would be specified as a hostname or IP address by the user */ #define

SERVER

"131.107.1.121"

struct sockaddr_in srv_addr,cli_addr; LPSERVENT srv_info; LPHOSTENT host_info; SOCKET cli_sock; . . /* Create client-side datagram socket */ cli_sock=socket(PF_INET,SOCK_DGRAM); if (cli_sock==INVALID_SOCKET){ sprintf(buf,"Windows Sockets error %d: Couldn’t create socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } cli_addr.sin_family=AF_INET; cli_addr.sin_addr.s_addr=INADDR_ANY; cli_addr.sin_port=0; /* no specific local port req’d */ /* Bind local socket */ if (bind(cli_sock,(LPSOCKADDR)&cli_addr,sizeof(cli_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t bind socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); }

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/* Resolve port information for TFTP service */ srv_info=getservbyname("tftp","udp"); if (srv_info== NULL) { sprintf(buf,"Windows Sockets error %d: Couldn’t resolve TFTP service port.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } srv_addr.sin_family = AF_INET; srv_addr.sin_addr.s_addr = inet_addr(SERVER); srv_addr.sin_port=srv_info->s_port; if (connect(cli_sock,(LPSOCKADDR)&srv_addr,sizeof(srv_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t connect socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } /* Client-server network interaction takes place here */ 6LQFHDFRQQHFWLRQOHVVFOLHQWVXFKDV7)73 ZLOOXQGRXEWHGO\EHGRLQJVXFFHVVLYHWUDQVPLVVLRQVZLWKWKHVHUYHUHVSHFLDOO\GXULQJORQJ WUDQVIHUV ZHKDYHFKRVHQWRFRQQHFWWKHVRFNHWDOORZLQJWKHXVHRIWKHVHQG DQGUHFY $3,VUDWKHUWKDQVHQGWR DQGUHFYIURP 7KH XVHRIFRQQHFW ZLWKGDWDJUDPVRFNHWVLVSXUHO\RSWLRQDO

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DSSOLFDWLRQGLGDUHFY ZLWKDEXIIHURIE\WHVLWZRXOGJHWDOOWKHGDWDDWRQFH 7KHUHIRUHDQDSSOLFDWLRQPXVWQRWPDNHDQ\DVVXPSWLRQVDERXWKRZGDWDZLOODUULYH$VHUYHUZKLFKH[SHFWVWRUHFHLYHE\WHVVKRXOGFDOO UHFY LQDORRSXQWLOLWKDVUHFHLYHGDOORIWKHGDWD

SOCKET int char char int

s; bytes_received; buffer[1000]; *buffer_ptr; buffer_length;

. . buffer_ptr = buffer; buffer_length = sizeof(buffer); /* Receive all outstanding data on socket s */ do { bytes_received = recv(s, buffer_ptr, buffer_length, 0); if (bytes_received == SOCKET_ERROR) { sprintf(buf,"Windows Sockets error %d: Error while receiving data.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } buffer_ptr += bytes_received; buffer_length -= bytes_received; } while (buffer_length > 0); /LNHZLVHDQDSSOLFDWLRQZKLFKZDQWVWRVHQGE\WHVVKRXOGVHQG LQDORRSXQWLODOORIWKHGDWDKDVEHHQVHQW

SOCKET int char char int

s; bytes_sent; buffer[1000]; *buffer_ptr; buffer_length;

buffer_ptr = buffer; buffer_length = sizeof(buffer); /* Enter send loop until all data in buffer is sent */

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do { bytes_sent = send(s, buffer_ptr, buffer_length, 0); if (bytes_sent == SOCKET_ERROR) { sprintf(buf,"Windows Sockets error %d: Error while sending data.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_app(); } buffer_ptr += bytes_sent; buffer_length -= bytes_sent; } while (buffer_length > 0);

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SOCKET SOCKADDR_IN int BYTE int

s; remoteAddr; remoteAddrLength = sizeof(remoteAddr); buffer[1024]; bytesReceived;

for ( ; ; ) { /* Receive a datagram on socket s */

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bytesReceived = recvfrom( s, buffer, sizeof(buffer),0, (PSOCKADDR)&remoteAddr, &remoteAddrLength ); /* Echo back to the server as long as bytes were received */ if ( bytesReceived != SOCKET_ERROR || sendto( s, buffer, bytesRecieved, 0, (PSOCKADDR)&remoteAddr, remoteAddrLength ) == SOCKET_ERROR ){ sprintf(buf,"Windows Sockets error %d: Error while sending data.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } } $VPHQWLRQHGHDUOLHULWLVSRVVLEOHWRFRQQHFW DGDWDJUDPVRFNHW2QFHDGDWDJUDPVRFNHWLVFRQQHFWHGDOOGDWDLVVHQWDQGUHFHLYHGIURP WKHUHPRWHDGGUHVVWRZKLFKWKHGDWDJUDPLVFRQQHFWHGVRLWLVSRVVLEOHWRXVHWKHVHQG DQGUHFY $3,VRQFRQQHFWHGGDWDJUDPVRFNHWV

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LINGER INT SOCKET

lingerInfo; err; s;

/* First set the linger timeout on the socket to 0. /* cause the connection to be reset. */

This will */

lingerInfo.l_onoff = 1;

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lingerInfo.l_linger = 0; setsockopt( s, SOL_SOCKET, SO_LINGER, (char *)&lingerInfo,sizeof(lingerInfo) ); closesocket(s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

SOCKET INT BYTE

s; err; buffer[1024];

err = shutdown( s , 1 ); if ( err == SOCKET_ERROR ) { sprintf(buf,"Windows Sockets error %d: Error during shutdown.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } /* Receive the rest of the pending data */ while ( (err = recv( s, buffer, sizeof(buffer), 0 ) != 0 ) { if ( err == SOCKET_ERROR ) { sprintf(buf,"Windows Sockets error %d: Error while receiving data.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } . . /* do something with the data we received. */ . . }

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Page 31 of 50 we can safely close now */

closesocket( s ); 1RWHWKDWLQWKLVH[DPSOHWKHDSSOLFDWLRQNHHSVFDOOLQJUHFY XQWLOLWUHWXUQV]HURE\WHVUHFHLYHG,IDQDSSOLFDWLRQFORVHVDVRFNHWDQGWKHUHLV GDWDDYDLODEOHWREHUHFHLYHGRUGDWDODWHUDUULYHVWKHQWKHV\VWHPZLOODERUWWKHFRQQHFWLRQDQGWKURZRXWWKHGDWDVLQFHWKHUHLVQRERG\WR JLYHWKHGDWDWR:HOOEHKDYHGDSSOLFDWLRQVVKRXOGHQVXUHWKDWWKH\UHFHLYHDOOGDWDEHIRUHFORVLQJDVRFNHW

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/* Static IP address for remote server for example. In reality, this would be specified as a hostname or IP address by the user */ #define #define #define

SERVER

"131.107.1.121"

SOCKET_MESSAGE SERVER_PORT

WM_USER+1 4000

struct sockaddr_in srv_addr; SOCKET cli_sock; . . . /* Create client-side socket */ cli_sock=socket(PF_INET,SOCK_STREAM,0); if (cli_sock==INVALID_SOCKET){ sprintf(buf, "Windows Sockets error %d: couldn’t open socket.", WSAGetLastError()); MessageBox(hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } srv_addr.sin_family = AF_INET; srv_addr.sin_addr.s_addr = inet_addr(SERVER); srv_addr.sin_port=SERVER_PORT; /* Connect to server */ if (connect(cli_sock,(LPSOCKADDR)&srv_addr,sizeof(srv_addr))==SOCKET_ERROR){ sprintf(buf,"Windows Sockets error %d: Couldn’t connect socket.", WSAGetLastError()); MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } /* Set up async select on FD_READ, FD_WRITE, and FD_CLOSE events */ err = WSAAsyncSelect(cli_sock, hWnd, SOCKET_MESSAGE, FD_READ|FD_WRITE|FD_CLOSE); if (err == SOCKET_ERROR) { sprintf(buf,"Windows Sockets error %d: WSAAsyncSelect failure.", WSAGetLastError());

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MessageBox (hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } :KHQRQHRIWKHVSHFLILHGQHWZRUNHYHQWVRFFXUVWKHVSHFLILHGZLQGRZKDQGOHK:QGUHFHLYHVDPHVVDJHFRQWDLQLQJDZ0VJRI 62&.(7B0(66$*(7KHZ3DUDPILHOGRIWKHPHVVDJHZLOOKDYHWKHVRFNHWKDQGOHDQGO3DUDPFRQWDLQVWZRSLHFHVRILQIRUPDWLRQWKHORZ ZRUGFRQWDLQVWKHHYHQWWKDWRFFXUUHG)'B5($')'B:5,7(RU)'B&/26( DQGWKHKLJKZRUGFRQWDLQVDQHUURUFRGHRULIWKHUHZDVQR HUURU&RGHVLPLODUWRWKHIROORZLQJIUDJPHQWZKLFKZRXOGEHORQJLQDQDSSOLFDWLRQ VPDLQZLQGRZSURFHGXUHPD\EHXVHGWRLQWHUSUHWD PHVVDJHIURP:6$$V\QF6HOHFW

long FAR PASCAL _export WndProc(HWND hWnd, UINT message, UINT wParam, LONG lParam) { INT err; switch (message) { case ...: /* handle Windows messages */ . . . case SOCKET_MESSAGE: /* A network event has occurred on our socket. Determine which network event occurred. */ switch (WSAGETSELECTEVENT(lParam)) { case FD_READ: /* Data arrived. Receive it. */ err = recv(cli_sock, Buffer, BufferLength, 0); if (WSAGetLastError() == WSAEWOULDBLOCK) { /* We have already received the data. */ break; } if (err == SOCKET_ERROR) { sprintf(buf, "Windows Sockets error %d: receive error.", WSAGetLastError()); MessageBox(hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } . . /* Do something useful with the data. */ . .

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break; case FD_WRITE: /* We can send data. */ err = send(cli_sock, Buffer, BufferLength, 0); if (err == SOCKET_ERROR) { if (WSAGetLastError() == WSAEWOULDBLOCK) { /* Send buffers overflowed. */ break; } sprintf(buf, "Windows Sockets error %d: send failed.", SAGetLastError()); MessageBox(hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } break; case FD_CLOSE: /* The remote closed the socket. */ closesocket(cli_sock); break; } break; }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

$V\QFKURQRXV'DWDEDVH5RXWLQHV -XVWDVVLPSOHQHWZRUNRSHUDWLRQVOLNHUHFY FDQEORFNIRUH[WHQGHGSHULRGVRIWLPHVRFDQWKHGDWDEDVHURXWLQHVOLNHJHWKRVWE\QDPH HVSHFLDOO\LVWKH\JRWKURXJK'16ZKLFKFDQUHTXLUHFRQVLGHUDEOHWLPHGXHWRWKHQHWZRUNDFWLYLW\LQYROYHG,QRUGHUWRDOORZZHOOEHKDYHG

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:LQGRZV$SSOLFDWLRQVWRXVHWKHGDWDEDVHURXWLQHVWKH:LQGRZV6RFNHWV$3,VXSSOLHVDV\QFKURQRXVYHUVLRQVRIWKHGDWDEDVHURXWLQHV7KHLU XVHLVVLPLODUWRWKHV\QFKURQRXVGDWDEDVHURXWLQHVZLWKWZRLPSRUWDQWH[FHSWLRQV

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,QRUGHUWRPDNHDQDV\QFKURQRXVGDWDEDVHFDOODQDSSOLFDWLRQSDVVHVLQLQIRUPDWLRQDERXWWKHFDOODZLQGRZKDQGOHWRUHFHLYHWKH FRPSOHWLRQPHVVDJHDPHVVDJHFRGHDQGDEXIIHUIRUWKHRXWSXWLQIRUPDWLRQ7KH:LQGRZV6RFNHWV$3,GHILQHVDFRQVWDQW 0$;*(7+2676758&7ZKLFKLVWKHPD[LPXPVL]HRIDKRVWHQWVWUXFWXUH$QDSSOLFDWLRQVKRXOGXVHDEXIIHURIWKLVVL]HWRSDVVWRWKH DV\QFKURQRXVGDWDEDVHURXWLQHVLQRUGHUWREHJXDUDQWHHGWKDWDOOWKHRXWSXWLQIRUPDWLRQZLOOILWLQLWVEXIIHU$FDOOWR :6$$V\QF*HW+RVW%\1DPH PD\EHDVIROORZV

#define GETHOST_MESSAGE BYTE HANDLE TaskHandle;

WM_USER+2

HostBuffer[MAXGETHOSTSTUCT];

/* Resolve hostname "hostname" asynchronously */ TaskHandle = WSAAsyncGetHostByName(hWnd, GETHOST_MESSAGE, "hostname", HostBuffer,

MAXGETHOSTST

if (TaskHandle == SOCKET_ERROR) { sprintf(buf, "Windows Sockets error %d: Hostname couldn’t be resolved.", WSAGetLastError()); MessageBox(hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } :6$$V\QF*HW+RVW%\1DPH DQGWKHRWKHUDV\QFKURQRXVGDWDEDVHURXWLQHVUHWXUQDWDVNKDQGOHZKLFKXQLTXHO\UHIHUVWRWKHRSHUDWLRQLQ SURJUHVV7KLVWDVNKDQGOHDOORZVDQDSSOLFDWLRQZKLFKPD\KDYHPXOWLSOHRXWVWDQGLQJDV\QFKURQRXVGDWDEDVHURXWLQHVWRDVVRFLDWHFRPSOHWLRQ PHVVDJHVZLWKWKHUHTXHVWVLQFHWKHWDVNKDQGOHLVUHWXUQHGLQWKHFRPSOHWLRQPHVVDJHDVZ3DUDP 7RUHFHLYHDQGSURFHVVWKHFRPSOHWLRQPHVVDJHDQDSSOLFDWLRQZLOOGRWKHIROORZLQJLQLWVZLQGRZSURFHGXUH

long FAR PASCAL _export WndProc(HWND hWnd, UINT message, UINT wParam, LONG lParam) { INT err;

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switch (message) { case ...: /* handle Windows messages */ . . . case GETHOST_MESSAGE: /* An asynchronous database routine completed. */ if (WSAGETASYNCERROR(lParam) != 0) { sprintf(buf, "Windows Sockets error %d: Hostname couldn’t be resolved.", WSAGetLastError()); MessageBox(hWnd,buf,"Windows Sockets Error",MB_OK); shutdown_appl(); } . . /* HostBuffer now contains a host buffer, use info from it. */ . . }

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7UDQVSRUW,QGHSHQGHQFH file:C:\TEMP\01becc72.htm

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:H YHIRFXVHGRQ7&3,3IRUPRVWRIWKLVDUWLFOHEXWZHSURPLVHGWRGHVFULEHKRZDQDSSOLFDWLRQFDQXVH:LQGRZV6RFNHWVRWKHUWUDQVSRUW SURWRFROVLQ:LQGRZV17DQG&KLFDJR:H OOIRFXVRQWKHKLJKOLJKWVDQGWKHNH\IHDWXUHVWKDWGLIIHUHQWLDWHGLIIHUHQWWUDQVSRUWSURWRFROVDQGRQ WKHPHFKDQLVPVIRURSHQLQJVRFNHWVIRUXVHZLWKGLIIHUHQWWUDQVSRUWSURWRFROV $OWKRXJKWKHVHDUHQRWH[SOLFLWO\DGGUHVVHGLQWKH:LQGRZV6RFNHWVVSHFLILFDWLRQWKHIDFWWKDWWKHIXQGDPHQWDOMRERIDWUDQVSRUWSURWRFROLV GDWDWUDQVIHUDORQJZLWKWKHIDFWWKDW:LQGRZV6RFNHWVSURYLGHVDULFKLQWHUIDFHIRUORZOHYHOGDWDWUDQVIHULQDSSOLFDWLRQVPDNHWKHLQWHUIDFH WR:LQGRZV6RFNHWVRYHUGLIIHUHQWWUDQVSRUWSURWRFROVTXLWHIHDVLEOH,QIDFWKDYLQJDFRPPRQZHOONQRZQ$3,LQWHUIDFHDOORZVDSSOLFDWLRQV WREHSRUWHGTXLFNO\EHWZHHQGLIIHUHQWWUDQVSRUWSURWRFROVDQGWKHUHDUHVHYHUDOVXFFHVVIXOH[DPSOHVRIWKLV %HFDXVHRIWKHDUFKLWHFWXUHRIWKH:LQGRZV6RFNHWVFRPSRQHQWVRI:LQGRZV17DQG&KLFDJRDOOVXSSRUWHGWUDQVSRUWVDUHDFFHVVHGWKURXJK WKHVDPH'//:62&.'//,QIDFWDVLQJOHDSSOLFDWLRQPD\VLPXOWDQHRXVO\XVHVRFNHWVRIGLIIHUHQWWUDQVSRUWSURWRFROV $QDSSOLFDWLRQXVHVWKHSDUDPHWHUVWRWKHVRFNHW $3,WRVSHFLI\WKHSURWRFROLWGHVLUHV)RUH[DPSOHD7&3VRFNHWLVRSHQHGZLWK

s_tcp = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP ); ZKLOHDQ63;VRFNHWLVRSHQHGZLWK

s_spx = socket( AF_IPX, SOCK_SEQPACKET, NSPROTO_SPX ); $IWHURSHQLQJDVRFNHWIRUDVSHFLILFSURWRFRODOODFWLRQVSHUIRUPHGRQWKHVRFNHWJRWKURXJKWKHVSHFLILHGSURWRFRO,QWKHDERYHH[DPSOHLI WKHDSSOLFDWLRQGLGDOLVWHQ RQWKHVBWFSVRFNHWEXWQRWRQWKHVBVS[VRFNHWLWZRXOGUHFHLYHLQFRPLQJFRQQHFWVWKURXJK7&3EXWQRWUHFHLYH LQFRPLQJFRQQHFWVWKURXJK63;

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