我编写了有关套接字的代码，当客户端发送消息或客户端执行CTRL + C时，我无法阻止服务器关闭
服务器关闭。
Server.c：
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h>
#define PORT 8888
#define BACKLOG 10
#define LOOP(i, n) for((i) = 0; (i) < (n); (i)++)
#define BUFFSIZE 6500
int create_fd( struct sockaddr_in *server );
int bind_fd ( struct sockaddr_in *server, int servSocket );
int list_fd( int servSocket );
int accept_fd( struct sockaddr_in *server, int servSocket );
int select_fd ( fd_set *readfds, int max_sd );
ssize_t send_fd( int new_fd, const char *const msg );
int main( void ){
const char msg[BUFFSIZE] = "Server is On\n";
char recive[BUFFSIZE];
int servSocket ,clientSocket ,i ,sd;
int client_socket_max[30] = { 0 } , max_clients = 30;
int max_sd;
ssize_t valread;
struct sockaddr_in server;
for (i = 0; i < max_clients; i++)
{
client_socket_max[i] = 0;
}
//set of socket descriptors
fd_set readfds;
size_t addr_size = sizeof(server);
//create
servSocket = create_fd( &server );
//bind the socket to localhost port 8888
bind_fd(&server, servSocket );
//listen the socket to localhost port 8888
printf("\tServer is On\nListener on port %d \n", PORT);
list_fd( servSocket );
//accept the incoming connection
printf( "\n\tWaiting for connections ...\n" );
while(1){
//clear the socket set
FD_ZERO(&readfds);
//add master socket to set
FD_SET(servSocket, &readfds);
max_sd = servSocket;
//add child sockets to set
LOOP( i, max_clients ){
//socket descriptor
sd = client_socket_max[i];
//if valid socket descriptor then add to read list
if(sd > 0){
FD_SET( sd , &readfds);
}
//highest file descriptor number, need it for the select function
if(sd > max_sd){
max_sd = sd;
}
}
//wait for an activity on one of the sockets , timeout is NULL , so wait indefinitely
select_fd( &readfds, max_sd );
//select( max_sd + 1 , &readfds , NULL , NULL , NULL);
//If something happened on the master socket , then its an incoming connection
if ( FD_ISSET( servSocket, &readfds ) ){
clientSocket = accept_fd( &server, servSocket );
//inform user of socket number - used in send and receive commands
printf("New connection , socket fd is %d , ip is : %s , port : %d \n" , clientSocket , inet_ntoa(server.sin_addr) , ntohs(server.sin_port));
//send new connection greeting msg
send_fd( clientSocket, msg );
/*if( send(clientSocket, msg, strlen(msg), 0) != (long int)strlen(msg) ){
perror("send");
}*/
puts("Welcome msg sent successfully");
//add new socket to array of sockets
LOOP( i, max_clients ){
//if position is empty
if( client_socket_max[i] == 0 ){
client_socket_max[i] = clientSocket;
printf("Adding to list of sockets as %d\n" , i);
break;
}
}
}
//else its some IO operation on some other socket :)
LOOP( i, max_clients ){
sd = client_socket_max[i];
if (FD_ISSET( sd , &readfds)){
//Check if it was for closing , and also read the incoming msg
if (( valread = read( sd , recive, 1024)) == 0){
//Somebody disconnected , get his details and print
getpeername(sd , (struct sockaddr*)&server , (socklen_t*)&addr_size);
printf("Host disconnected , ip %s , port %d \n" , inet_ntoa(server.sin_addr) , ntohs(server.sin_port));
//Close the socket and mark as 0 in list for reuse
close( sd );
client_socket_max[i] = 0;
}else{//Echo back the msg that came in
//set the string terminating NULL byte on the end of the data read
recive[valread] = '\0';
send(sd , recive , strlen(recive) , 0 );
}
}
}
}
close( servSocket );
}
int create_fd( struct sockaddr_in *server ){
int opt = 1;
int servSocket = socket(AF_INET , SOCK_STREAM , 0);
if (servSocket == -1 ){
printf("Error, socket()\n");
fprintf(stderr, "socket: %s (%d)\n", strerror(errno), errno);
exit ( EXIT_FAILURE );
}
//set master socket to allow multiple connections , this is just a good habit, it will work without this
if( setsockopt(servSocket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0 ){
perror("setsockopt");
exit(EXIT_FAILURE);
}
//type of socket created
server->sin_family = AF_INET;
server->sin_addr.s_addr = INADDR_ANY;
server->sin_port = htons( PORT );
//printf("socket() \tOK\n");
return servSocket;
}
int bind_fd ( struct sockaddr_in *server, int servSocket ){
int bindfd = bind( servSocket, (struct sockaddr *)server, sizeof(*server) );
if (bindfd == -1 ){
printf("Error, bind(), check line 34\n");
fprintf(stderr, "bind: %s (%d)\n", strerror(errno), errno);
exit ( EXIT_FAILURE );
}else{
//printf("bind() \t\tOK\n");
return bindfd;
}
}
int list_fd( int servSocket ){
int listfd = listen(servSocket, BACKLOG);
if (listfd == -1 ){
printf("Error, listen()\n");
fprintf(stderr, "listen: %s (%d)\n", strerror(errno), errno);
exit ( EXIT_FAILURE );
}else{
//printf("listen() \tOK\n");
return listfd;
}
}
int accept_fd( struct sockaddr_in *server, int servSocket ){
int new_fd;
socklen_t addr_size = sizeof( server );
new_fd = accept(servSocket, (struct sockaddr *)server, (socklen_t*)&addr_size);
if (new_fd == -1 ){
printf("Error, accept()\n");
fprintf(stderr, "accept: %s (%d)\n", strerror(errno), errno);
exit ( EXIT_FAILURE );
}else{
//printf("accept() \tOK\n");
return new_fd;
}
}
int select_fd ( fd_set *readfds, int max_sd ){
int activity = select( max_sd + 1 , readfds , NULL , NULL , NULL);
if ((activity < 0) && (errno!=EINTR)){
printf("select error");
exit ( EXIT_FAILURE );
}else{
return activity;
}
}
ssize_t send_fd( int new_fd, const char *const msg ){
size_t len = strlen(msg);
ssize_t sendfd;
sendfd = send( new_fd, msg, len, 0 );
if (sendfd == -1 ){
printf("Error, write()\n");
fprintf(stderr, "recv: %s (%d)\n", strerror(errno), errno);
exit ( EXIT_FAILURE );
}else{
printf("write() \tOK\n");
printf("Client sent:\t%s", msg );
return sendfd;
}
}
Client.c：
#include <stdio.h>
#include <string.h> //strlen
#include <stdlib.h>
#include <errno.h>
#include <unistd.h> //close
#include <arpa/inet.h> //close
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h> //FD_SET, FD_ISSET, FD_ZERO macros
#define PORT 8888
#define BUFFSIZE 6500
int create_fd( struct sockaddr_in server );
int connect_fd( const int servSocket, struct sockaddr_in *server );
int opt = 1;
int main ( void ){
struct sockaddr_in server;
char recivemsg[BUFFSIZE];
char sendmsg[BUFFSIZE];
memset( recivemsg, 0, sizeof(*recivemsg) );
memset( sendmsg, 0, sizeof(*sendmsg) );
int servSocket = socket(AF_INET , SOCK_STREAM , 0);
if (servSocket == -1 ){
printf("Error, socket()\n");
fprintf(stderr, "socket: %s (%d)\n", strerror(errno), errno);
exit ( EXIT_FAILURE );
}
//set master socket to allow multiple connections , this is just a good habit, it will work without this
if( setsockopt(servSocket, SOL_SOCKET, SO_REUSEADDR, (char *)&opt, sizeof(opt)) < 0 ){
perror("setsockopt");
exit(EXIT_FAILURE);
}
//type of socket created
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons( PORT );
if ( ( connect( servSocket, ( struct sockaddr* )&server, sizeof( server ) ) ) < 0 ){
printf("Error, connect()\n");
fprintf(stderr, "connect: %s (%d)\n", strerror(errno), errno);
exit( EXIT_FAILURE );
}
if ( recv( servSocket, recivemsg, sizeof ( recivemsg ), 0 ) < 0 ){
printf("Error, recv()\n");
fprintf(stderr, "recv: %s (%d)\n", strerror(errno), errno);
exit( EXIT_FAILURE );
}
printf("Send a msg to the Server:> ");
fgets(sendmsg, BUFFSIZE, stdin );
if ( send( servSocket, sendmsg, sizeof ( sendmsg ), 0 ) < 0 ){
printf("Error, send()\n");
fprintf(stderr, "send: %s (%d)\n", strerror(errno), errno);
exit( EXIT_FAILURE );
}
close( servSocket );
}
答案 0 :(得分：1)
代码中存在一些问题，可能会导致服务器程序过早退出。
最重要的是，您不要检查来自read或send呼叫的错误。
如果read调用失败，它将返回-1，您无需检查（这将导致您使用-1作为数组receive的索引，这超出范围并导致undefined behavior）。这继而导致您以断开的连接调用send，这将导致操作系统向您的进程发送SIGPIPE信号。
SIGPIPE的默认行为是终止该过程。
处理此问题的常用方法是忽略 SIGPIPE信号，因为这样send会返回一个错误（它返回-1和{{ 1}}设置为errno）。
处理错误（来自EPIPE或read的常见方法是简单地send连接结束。那是因为大多数错误根本无法恢复。