3 * Copyright (C) 2001-2003 Simone Piccardi
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or (at
8 * your option) any later version.
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 /****************************************************************
22 * Elementary TCP server for echo service (port 7)
25 * Author: Simone Piccardi
28 * Usage: echod -h give all info
30 ****************************************************************/
32 * Include needed headers
34 #include <sys/types.h> /* primitive system data types */
35 #include <unistd.h> /* unix standard library */
36 #include <arpa/inet.h> /* IP addresses conversion utilities */
37 #include <sys/socket.h> /* socket constants, types and functions */
38 #include <stdio.h> /* standard I/O library */
39 #include <time.h> /* date and time constants, types and functions */
40 #include <syslog.h> /* syslog system functions */
41 #include <signal.h> /* signal constants, types and functions */
42 #include <errno.h> /* error definitions and routines */
43 #include <string.h> /* C strings library */
44 #include <stdlib.h> /* C standard library */
50 int demonize = 1; /* daemon use option: default is daemon */
51 int debugging = 0; /* debug info printing option: default is no debug */
52 /* Subroutines declaration */
54 void ServEcho(int sockfd);
55 void PrintErr(char * error);
56 /* Program beginning */
57 int main(int argc, char *argv[])
60 * Variables definition
64 struct sockaddr_in serv_add;
66 * Input section: decode parameters passed in the calling
70 opterr = 0; /* don't want writing to stderr */
71 while ( (i = getopt(argc, argv, "hdi")) != -1) {
77 printf("Wrong -h option use\n");
87 case '?': /* unrecognized options */
88 printf("Unrecognized options -%c\n",optopt);
90 default: /* should not reached */
94 /* ***********************************************************
96 * Options processing completed
100 * ***********************************************************/
101 /* install SIGCHLD handler */
102 Signal(SIGCHLD, HandSigCHLD); /* establish handler */
104 if ( (list_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
105 perror("Socket creation error");
108 /* initialize address */
109 memset((void *)&serv_add, 0, sizeof(serv_add)); /* clear server address */
110 serv_add.sin_family = AF_INET; /* address type is INET */
111 serv_add.sin_port = htons(7); /* echo port is 7 */
112 serv_add.sin_addr.s_addr = htonl(INADDR_ANY); /* connect from anywhere */
114 if (bind(list_fd, (struct sockaddr *)&serv_add, sizeof(serv_add)) < 0) {
115 perror("bind error");
118 /* release privileges and go daemon */
119 if (setgid(65534) !=0) { /* first give away group privileges */
120 perror("cannot give away group privileges");
123 if (setuid(65534) !=0) { /* and only after user ... */
124 perror("cannot give away user privileges");
127 if (demonize) { /* go daemon */
128 openlog(argv[0], 0, LOG_DAEMON); /* open logging */
129 if (daemon(0, 0) != 0) {
130 perror("cannot start as daemon");
135 if (listen(list_fd, BACKLOG) < 0 ) {
136 PrintErr("listen error");
139 /* handle echo to client */
141 /* accept connection */
142 if ( (conn_fd = accept(list_fd, NULL, NULL)) < 0) {
143 PrintErr("accept error");
146 /* fork to handle connection */
147 if ( (pid = fork()) < 0 ){
148 PrintErr("fork error");
151 if (pid == 0) { /* child */
152 close(list_fd); /* close listening socket */
153 ServEcho(conn_fd); /* handle echo */
155 } else { /* parent */
156 close(conn_fd); /* close connected socket */
159 /* normal exit, never reached */
163 * routine to print usage info and exit
166 printf("Elementary echo server\n");
168 printf(" echod [-h] \n");
169 printf(" -h print this help\n");
170 printf(" -d print debug info\n");
171 printf(" -i use interactively\n");
175 * routine to handle echo for connection
177 void ServEcho(int sockfd) {
178 char buffer[MAXLINE];
180 char debug[MAXLINE+20];
182 /* main loop, reading 0 char means client close connection */
183 while ( (nread = read(sockfd, buffer, MAXLINE)) != 0) {
184 nwrite = FullWrite(sockfd, buffer, nread);
186 PrintErr("write error");
192 * routine to print error on stout or syslog
194 void PrintErr(char * error) {
195 if (demonize) { /* daemon mode */
196 syslog(LOG_ERR, "%s: %m", error); /* log string and error message */