Extend to socket again.

The following is a Linux and socket chat program I recently studied using C. To learn epoll, epoll has a lot of socket statements, so it jumps to the C side.

Server. c

# Include <stdio. h> # include <stdlib. h> # include <string. h> # include <errno. h> # include <sys/socket. h> # include <ARPA/inet. h> # include <netinet/in. h> # include <sys/types. h> # include <unistd. h> # define buflen 10 # define ser_addr "127.0.0.1" # Define port 8080 # define max_conn 200int main (INT argc, char ** argv) {int sockfd, newfd; struct sockaddr_in s_addr, c_addr; char Buf [buflen]; socklen_t Len; unsigned int por T = 8080, listnum = 200;/* resume socket */If (sockfd = socket (af_inet, sock_stream, 0) =-1) {perror ("socket"); exit (errno);} else {printf ("socket create success! \ N ");}/* set the length of the listener queue */printf (" listnum = % d ", listnum);/* set the Server IP Address */bzero (& s_addr, sizeof (s_addr); s_addr.sin_family = af_inet; s_addr.sin_port = htons (port); printf ("Port = % d \ n", Port); If (ser_addr) latency = inet_addr (ser_addr); else s_addr.sin_addr.s_addr = inaddr_any; printf ("socket_addr.addr = % d", s_addr.sin_addr.s_addr ); /* bind the address and port to the socket */If (BIND (sockfd, (struct sockaddr *) & S _ ADDR, sizeof (struct sockaddr) =-1) {perror ("bind"); exit (errno);} else {printf ("bind success! \ N ");}/* Listen to the local port */If (Listen (sockfd, listnum) =-1) {perror (" listen "); exit (errno );} else printf ("the server is listening! \ N "); While (1) {printf (" ************ chat start ********* \ n "); len = sizeof (struct sockaddr); If (newfd = accept (sockfd, (struct sockaddr *) & c_addr, & Len) =-1) {printf ("A Client Connected \ n"); perror ("accept"); exit (errno);} else printf ("the client chatting with you is: % s: % d \ n ", inet_ntoa (c_addr.sin_addr), ntohs (c_addr.sin_port); While (1) {_ retry: /***** send message ***/bzero (BUF, buflen); printf ("Enter the message of the sender:");/* fgets function: read Buf from stream LEN-1 characters */fgets (BUF, buflen, stdin);/* print the message sent * // fputs (BUF, stdout); If (! Strncasecmp (BUF, "quit", 4) {printf ("server request to terminate the chat! \ N "); break;}/* If the input string is only" \ n ", that is, press enter, then the new input */If (! Strncmp (BUF, "\ n", 1) {printf ("the input character is only a carriage return. This is incorrect !!! \ N "); goto _ retry;}/* If the Buf contains '\ n', use strlen (BUF)-1, remove '\ n' */If (strchr (BUF,' \ n') Len = Send (newfd, Buf, strlen (BUF)-1, 0 ); /* If the Buf does not contain '\ n', use the actual Buf length strlen (BUF) */else Len = Send (newfd, Buf, strlen (BUF), 0 ); if (LEN> 0) printf ("message sent successfully, the number of bytes sent this time is % d \ n", Len); else {printf ("Message failed to be sent! \ N "); break;}/***** receive message ******/bzero (BUF, buflen); Len = Recv (newfd, Buf, buflen, 0); If (LEN> 0) printf ("The message sent from the client is % S. The total number of bytes is % d \ n", Buf, Len ); else {If (LEN <0) printf ("failed to receive message! \ N "); else printf (" the client has exited and the chat has ended! \ N "); break;}/* close the chat socket */close (newfd);/* exit the server */printf (" whether the server exits the program: y-> yes; n-> NO? "); Bzero (BUF, buflen); fgets (BUF, buflen, stdin); If (! Strncasecmp (BUF, "Y", 1) {printf ("server exited! \ N "); break;}/* close the server socket */close (sockfd); Return 0 ;}

Client. c

# Include <stdio. h> # include <stdlib. h> # include <errno. h> # include <string. h> # include <sys/socket. h> # include <sys/types. h> # include <ARPA/inet. h> # include <netinet/in. h> # include <unistd. h> # define buflen 100int main (INT argc, char ** argv) {int sockfd; struct sockaddr_in s_addr; socklen_t Len; unsigned int Port = 8080; char Buf [buflen]; /* resume socket */If (sockfd = socket (af_inet, sock_stream, 0) =-1) {per Ror ("socket"); exit (errno);} else printf ("socket create success! \ N ");/* set the Server IP Address */bzero (& s_addr, sizeof (s_addr); s_addr.sin_family = af_inet; s_addr.sin_port = htons (port ); char * server_addr = "127.0.0.1"; if (inet_aton (server_addr, (struct in_addr *) & Dr) = 0) {perror (server_addr); exit (errno );} printf ("fingerprint = % d", s_addr.sin_addr.s_addr);/* start to connect to the server */If (connect (sockfd, (struct sockaddr *) & s_addr, sizeof (struct sockaddr ))! = 0) {printf ("Connect failed"); perror ("Connect"); exit (errno);} else printf ("Connect success! % D \ n ", errno); printf (" Enter the while loop "); While (1) {printf (" while "); /** receive message **/bzero (BUF, buflen); Len = Recv (sockfd, Buf, buflen, 0); If (LEN> 0) printf ("the message sent by the server is % S. The total number of bytes is % d \ n", Buf, Len); else {printf ("else "); if (LEN <0) printf ("failed to receive message! \ N "); else printf (" the server has exited and the chat has ended! \ N "); break;} _ retry:/*** send message ***/bzero (BUF, buflen); printf (" Enter the message sent to the other party: ");/* fgets function: Read the BUFLEN-1 characters from the stream */fgets (BUF, buflen, stdin);/* print the message sent * // fputs (BUF, stdout); If (! Strncasecmp (BUF, "quit", 4) {printf ("client request to terminate the chat! \ N "); break;}/* If the input string is only '\ n', that is, press enter, re-enter */If (! Strncmp (BUF, "\ n", 1) {printf ("the input character is only a carriage return. This is incorrect !!! \ N "); goto _ retry;} printf (" % s ", Buf);/* If the Buf contains '\ n', use strlen (BUF)-1, remove '\ n' */If (strchr (BUF,' \ n') {printf ("start to send"); Len = Send (sockfd, Buf, strlen (BUF)-1, 0);}/* If the Buf does not contain \ n, use the real length of the Buf strlen (BUF) */else Len = Send (sockfd, buf, strlen (BUF), 0); printf ("Len = % d", Len); If (LEN> 0) printf ("message sent successfully, the total number of bytes sent this time is % d \ n ", Len); else {printf (" message sending failed! \ N "); break;}/* close connection */close (sockfd); Return 0 ;}

　　

In addition, I recently read "C and pointer" and read it intermittently. Record an interesting one today

For Constants

Int const;

Const int;

Both statements are normative.

Int * PI; Pi is a common pointer to an integer.

Int const * CPI; PCI is a pointer to an integer constant. You can modify the pointer value but cannot modify the value it points.

Int * const CPI; CPI is a constant pointer to an integer. A pointer is a constant and its value cannot be modified, but you can modify the integer it points.

Int const * const CPCI; both the pointer and the value pointed to by the pointer are constants and cannot be modified.