C-language TCP and UDP clients and servers

Are the simplest to remember.

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The simplest server for TCP:

intMainintargcConst Char*argv[]) {    intLISTENFD, ACCEPTFD; structsockaddr_in sin, cin;    Socklen_t Clen; Charbuf[1024x768];    Signal (SIGCHLD, sig_ign); LISTENFD= Socket (pf_inet, Sock_stream,0); Sin.sin_family=pf_inet; Sin.sin_port= Htons (Atoi (argv[2])); Sin.sin_addr.s_addr= Inet_addr (argv[1]); Bind (LISTENFD, (structSOCKADDR *) &sin,sizeof(sin)); Listen (LISTENFD,5);  while(1) {Clen=sizeof(CIN); printf ("listen ... \ n"); ACCEPTFD= Accept (LISTENFD, (structSOCKADDR *) &cin, &Clen); printf ("Client%s%d connect\n", Inet_ntoa (CIN.SIN_ADDR), Ntohs (Cin.sin_port)); if(fork () = =0) {close (LISTENFD);  while(1) {bzero (buf,sizeof(BUF)); if(Recv (ACCEPTFD, buf,sizeof(BUF),0) ==0) {printf ("Client%s%d exit\n", Inet_ntoa (CIN.SIN_ADDR), Ntohs (Cin.sin_port)); Exit (0); } printf ("recv (%s%d):%s\n", Inet_ntoa (CIN.SIN_ADDR), Ntohs (Cin.sin_port), buf);    }} close (ACCEPTFD); }    return 0;}

The simplest client for TCP:

intMainintargcConst Char*argv[]) {    intCFD = socket (pf_inet, Sock_stream,0); structsockaddr_in cin; Charbuf[1024x768]; Cin.sin_family=pf_inet; Cin.sin_port= Htons (Atoi (argv[2])); Cin.sin_addr.s_addr= Inet_addr (argv[1]); Connect (CFD, (structSOCKADDR *) &cin,sizeof(CIN)); printf ("Connect IP (%s) port (%s) server ok\n", argv[1], argv[2]); if(fork () = =0)    {         while(1) {bzero (buf,sizeof(BUF)); Recv (CfD, buf,sizeof(BUF),0); printf ("recv:%s\n", BUF); }    }     while(1) {fgets (buf,sizeof(BUF), stdin); Buf[strlen (BUF)-1] =' /'; Send (CFD, buf, strlen (BUF)+1,0); }    return 0;}

The simplest server for UDP:

int main (int argc, const char *argv[]) {int sfd;struct sockaddr_in sin, Cin;char buf1[1024], buf2[1024], Buf3[1024];socklen _t CLEN;SFD = socket (pf_inet, SOCK_DGRAM, 0); sin.sin_family = Pf_inet;sin.sin_port = Htons (atoi (argv[2)); Sin.sin_ ADDR.S_ADDR = inet_addr (argv[1]), Bind (SFD, (struct sockaddr *) &sin, sizeof (SIN)), if (fork () = = 0) {while (1) {Clen = sizeof (CIN); bzero (buf1, sizeof (BUF1)); Recvfrom (SFD, buf1, sizeof (BUF1), 0, (struct sockaddr *) &cin, &clen); printf ("Recvfrom:%s%d%s\n", Inet_ntoa (CIN.SIN_ADDR), Ntohs (Cin.sin_port), BUF1);}} while (1) {fscanf (stdin, "%s%s%s", Buf1, Buf2, buf3); cin.sin_family = Pf_inet;cin.sin_port = Htons (atoi (BUF2)); Cin.sin_ ADDR.S_ADDR = inet_addr (BUF1); SendTo (SFD, buf3, strlen (buf3) +1, 0, (struct sockaddr *) &cin, sizeof (CIN));} return 0;}

The simplest client for UDP:

int main (int argc, const char *argv[]) {int sfd;struct sockaddr_in Cin;char buf1[1024], buf2[1024], buf3[1024];socklen_t cl EN;SFD = socket (pf_inet, SOCK_DGRAM, 0), if (fork () = = 0) {while (1) {Clen = sizeof (CIN); bzero (buf1, sizeof (BUF1)); Recvfrom ( SFD, buf1, sizeof (BUF1), 0, (struct sockaddr *) &cin, &clen);p rintf ("Recvfrom:%s%d%s\n", Inet_ntoa (cin.sin_addr ), Ntohs (Cin.sin_port), BUF1);}} while (1) {fscanf (stdin, "%s%s%s", Buf1, Buf2, buf3); cin.sin_family = Pf_inet;cin.sin_port = Htons (atoi (BUF2)); Cin.sin_ ADDR.S_ADDR = inet_addr (BUF1); SendTo (SFD, buf3, strlen (buf3) +1, 0, (struct sockaddr *) &cin, sizeof (CIN));} return 0;}

The simplest server for ftp:

#define N 256void list (int connectfd) {DIR *dir;struct dirent *d;char buf[n];if ((Dir=opendir ((const char *) Get_current_ Dir_name ())) = = NULL) {perror ("Opendir"); exit (1);} while (D=readdir (dir)) = NULL) {if (d->d_name[0] = = '. ') {continue;} strcpy (buf, d->d_name); Send (CONNECTFD, buf, N, 0);} Closedir (dir);} void get (int connectfd, char *filename) {char buf[n]; FILE *fp;int n;if ((fp=fopen (filename, "r") = = NULL) {strcpy (buf, "no"), Send (CONNECTFD, buf, sizeof (BUF), 0);} strcpy (buf, "yes"); Send (CONNECTFD, buf, sizeof (BUF), 0), while (N=fread (buf, 1, sizeof (BUF), FP)) > 0) {Send (connectfd , buf, n, 0);} Fclose (FP);} void put (int connectfd, char *filename) {char buf[n]; FILE *fp;int n;if ((fp=fopen (filename, "r") = = NULL) {strcpy (buf, "no"); Send (CONNECTFD, buf, sizeof (BUF), 0); fp = fopen (fi Lename, "W"), while ((N=recv (CONNECTFD, buf, sizeof (BUF), 0)) > 0) {fwrite (buf, 1, N, FP);} Fclose (FP); return;} strcpy (buf, "yes"); Send (CONNECTFD, buf, sizeof (BUF), 0);} int main (int argc, const char *argv[]) {FILE *fp;iNT N, LISTENFD, CONNECTFD, i;struct sockaddr_in s, c;struct servent *sport;socklen_t Clen;char *LINEP = NULL, Buf[N], *arg [32];signal (SIGCHLD, sig_ign); if ((Fp=fopen ("/etc/ftp.conf", "r") = = NULL) {perror ("fopen"); exit (1);} if (Getline (&LINEP, &n, fp) = =-1) {perror ("getline"); exit (0);} Linep[strlen (LINEP)-1] = ' sport=getservbyname '; chdir (LINEP); if ((Myftp ("Perror", "tcp") = = = NULL) {getservbyname ); exit (1);} #ifdef debugprintf ("%d%s\n", N, Linep), #endifif ((Listenfd=socket (pf_inet, Sock_stream, 0)) = =-1) {perror ("socket"); Exit (1);} s.sin_family = Pf_inet;s.sin_port = sport->s_port; S.SIN_ADDR.S_ADDR = htonl (Inaddr_any); if (Bind (LISTENFD, (struct sockaddr *) &s, sizeof (s)) = =-1) {perror ("bind"); Exit (1);} Listen (LISTENFD, 5); while (1) {clen = sizeof (c); if (Connectfd=accept (LISTENFD, (struct sockaddr *) &c, &clen) = = -1) {perror ("accept"); exit (1);} if (fork () = = 0) {close (LISTENFD); recv (CONNECTFD, buf, sizeof (BUF), 0); Arg[0] = Strtok (buf, ""); for (I=1; Arg[i-1]!=null; i++) {Arg[i]=strtok (NULL, "");} if (strcmp (arg[0], "list") = = 0) {list (CONNECTFD);} if (strcmp (arg[0], "get") = = 0) {get (CONNECTFD, arg[1]);} if (strcmp (arg[0], "put") = = 0) {put (CONNECTFD, arg[1]);} Close (CONNECTFD); exit (0);} Close (CONNECTFD);}}

　　

　　

FTP is the simplest client device:

#define N 256void list (int connectfd) {DIR *dir;struct dirent *d;char buf[n];if ((Dir=opendir ((const char *) Get_current_ Dir_name ())) = = NULL) {perror ("Opendir"); exit (1);} while (D=readdir (dir)) = NULL) {if (d->d_name[0] = = '. ') {continue;} strcpy (buf, d->d_name); Send (CONNECTFD, buf, N, 0);} Closedir (dir);} void get (int connectfd, char *filename) {char buf[n]; FILE *fp;int n;if ((fp=fopen (filename, "r") = = NULL) {strcpy (buf, "no"), Send (CONNECTFD, buf, sizeof (BUF), 0);} strcpy (buf, "yes"); Send (CONNECTFD, buf, sizeof (BUF), 0), while (N=fread (buf, 1, sizeof (BUF), FP)) > 0) {Send (connectfd , buf, n, 0);} Fclose (FP);} void put (int connectfd, char *filename) {char buf[n]; FILE *fp;int n;if ((fp=fopen (filename, "r") = = NULL) {strcpy (buf, "no"); Send (CONNECTFD, buf, sizeof (BUF), 0); fp = fopen (fi Lename, "W"), while ((N=recv (CONNECTFD, buf, sizeof (BUF), 0)) > 0) {fwrite (buf, 1, N, FP);} Fclose (FP); return;} strcpy (buf, "yes"); Send (CONNECTFD, buf, sizeof (BUF), 0);} int main (int argc, const char *argv[]) {FILE *fp;iNT N, LISTENFD, CONNECTFD, i;struct sockaddr_in s, c;struct servent *sport;socklen_t Clen;char *LINEP = NULL, Buf[N], *arg [32];signal (SIGCHLD, sig_ign); if ((Fp=fopen ("/etc/ftp.conf", "r") = = NULL) {perror ("fopen"); exit (1);} if (Getline (&LINEP, &n, fp) = =-1) {perror ("getline"); exit (0);} Linep[strlen (LINEP)-1] = ' sport=getservbyname '; chdir (LINEP); if ((Myftp ("Perror", "tcp") = = = NULL) {getservbyname ); exit (1);} #ifdef debugprintf ("%d%s\n", N, Linep), #endifif ((Listenfd=socket (pf_inet, Sock_stream, 0)) = =-1) {perror ("socket"); Exit (1);} s.sin_family = Pf_inet;s.sin_port = sport->s_port; S.SIN_ADDR.S_ADDR = htonl (Inaddr_any); if (Bind (LISTENFD, (struct sockaddr *) &s, sizeof (s)) = =-1) {perror ("bind"); Exit (1);} Listen (LISTENFD, 5); while (1) {clen = sizeof (c); if (Connectfd=accept (LISTENFD, (struct sockaddr *) &c, &clen) = = -1) {perror ("accept"); exit (1);} if (fork () = = 0) {close (LISTENFD); recv (CONNECTFD, buf, sizeof (BUF), 0); Arg[0] = Strtok (buf, ""); for (I=1; Arg[i-1]!=null; i++) {Arg[i]=strtok (NULL, "");} if (strcmp (arg[0], "list") = = 0) {list (CONNECTFD);} if (strcmp (arg[0], "get") = = 0) {get (CONNECTFD, arg[1]);} if (strcmp (arg[0], "put") = = 0) {put (CONNECTFD, arg[1]);} Close (CONNECTFD); exit (0);} Close (CONNECTFD);}}

C-language TCP and UDP clients and servers