我想知道为什么我的程序运行但不像我预期的那样。我正在使用fork()创建客户端 - 服务器，但结果是：server2: success，但不是我想要的listening。我用gcc -o server2 server2.c
这是服务器端：
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/wait.h> // trap the child exits and prevent zombies
#include <signal.h> // trap the child exits and prevent zombies
#include <stdlib.h>
// signal handler calls waitpid()
void sigchld_handler(int signo)
{
while(waitpid(-1, NULL, WNOHANG) > 0);
}
// declares variabel
int main(int argc, char *argv[])
{
struct sockaddr_in sAddr;
int listensock;
int newsock;
char buffer[25];
int result;
int nread;
int pid;
int val;
// create socket that will accept connection
listensock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
// set our SO_REUSEADDR option
val = 1;
result = setsockopt(listensock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
if(result < 0){
perror("server1 multiplexing");
return 0;
}
// bind to local port and all addresses associated with the machine
sAddr.sin_family = AF_INET;
sAddr.sin_port = htons(1972);
sAddr.sin_addr.s_addr = INADDR_ANY;
result = bind(listensock, (struct sockaddr *) &sAddr, sizeof(sAddr));
if(result < 0){
perror("server2");
return 0;
}
// put the socket into listening mode for incoming connections
result = listen(listensock, 5);
if(result < 5){
perror("server2");
return 0;
}
// before start looping, we install our signal handler
signal(SIGCHLD, sigchld_handler);
// call accept() to block waiting for connection request from clients, after accept returns call fork() to create a new process
while(1){
newsock = accept(listensock, NULL, NULL);
if((pid = fork()) == 0){
// close listening socket, read char from client vice versa, close the socket and exit child process
printf("child process %i created.\n", getpid());
close(listensock);
nread = recv(newsock, buffer, 25, 0);
buffer[nread] = '\0';
printf("%s\n", buffer);
send(newsock, buffer, nread, 0);
close(newsock);
printf("child process %i finished.\n", getpid());
exit(0);
}else{
printf("child process error");
}
// parents process close
close(newsock);
}
}
这是客户：
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
void child_func(int childnum);
// main function
int main(int argc, char *argv[])
{
int nchildren = 1;
int pid;
int x;
if (argc > 1){
nchildren = atoi(argv[1]);
}
for (x=0; x < nchildren; x++){
if((pid = fork() == 0)){
child_func(x+1);
exit(0);
}
}
wait(NULL);
return 0;
}
void child_func(int childnum){
int sock;
struct sockaddr_in sAddr;
char buffer[25];
// create client socket and bind it to local pprt
memset((void *) &sAddr, 0, sizeof(struct sockaddr_in));
sAddr.sin_family = AF_INET;
sAddr.sin_addr.s_addr = INADDR_ANY;
sAddr.sin_port = 0;
sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
bind(sock, (const struct sockaddr *) &sAddr, sizeof(sAddr));
// Attempt to connect to whichever server is running on the local machine
sAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
sAddr.sin_port = htons(1972);
if (connect(sock, (const struct sockaddr *) &sAddr, sizeof(sAddr)) != 0){
perror("client");
return;
}
// send some character to the server and insert sleep() function
snprintf(buffer, 128, "data from client #%i.", childnum);
sleep(1);
printf("child #%i sent %zu chars\n", childnum, send(sock, buffer, strlen(buffer), 0));
sleep(1);
printf("child #%i received %zu chars\n", childnum, recv(sock, buffer, 25, 0));
//close connection
sleep(1);
close(sock);
}