Hok*_*rie 3 c sockets parent-child
我认为这可能是一个简单的解决方案，我只是想太多了。我正在编写一个非常基本的聊天程序，其中客户端和服务器轮流发送消息。现在，我只来回发送消息一次，然后客户端关闭套接字。该程序不必同时打开套接字，只要它可以像秋千一样来回切换即可，而不是真正的聊天程序，它可以同时接受双方的多个输入。
客户端中的 while 循环会保持打开状态吗？ while 循环的条件是什么？
我尝试了几种不同的条件，但没有一个起作用......它只是让它挂起。我还尝试注释掉close()服务器代码中的一些函数，但这也不起作用。
我还有一个小问题，即接收到的输入打印乱码，但我认为这是因为它在字符串数组中没有任何内容时打印字符串数组的内存地址......我只是不记得如何缩短它。哈哈。
服务器.c：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <signal.h>
#define PORT "3490" // The port users will be connecting to
#define BACKLOG 10 // How many pending connections queue will hold
char input[20];
char *pointer;
void sigchld_handler(int s)
{
while(waitpid(-1, NULL, WNOHANG) > 0);
}
// Get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(void)
{
int sockfd, new_fd; // Listen on sock_fd, new connection on new_fd
struct addrinfo hints, *servinfo, *p;
struct sockaddr_storage their_addr; // Connector's address information
socklen_t sin_size;
struct sigaction sa;
int yes = 1;
char s[INET6_ADDRSTRLEN];
int rv;
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE; // use my IP
if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// loop through all the results and bind to the first we can
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("server: socket");
continue;
}
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes,
sizeof(int)) == -1) {
perror("setsockopt");
exit(1);
}
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("server: bind");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "server: failed to bind\n");
return 2;
}
freeaddrinfo(servinfo); // All done with this structure
if (listen(sockfd, BACKLOG) == -1) {
perror("listen");
exit(1);
}
sa.sa_handler = sigchld_handler; // Reap all dead processes
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
if (sigaction(SIGCHLD, &sa, NULL) == -1) {
perror("sigaction");
exit(1);
}
printf("server: waiting for connections...\n");
sin_size = sizeof their_addr;
while((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) > 0) { // Main accept() loop
if (new_fd == -1) {
perror("accept");
continue;
}
inet_ntop(their_addr.ss_family,
get_in_addr((struct sockaddr *)&their_addr),
s, sizeof s);
printf("server: got connection from %s\n", s);
if (!fork()) { // this is the child process
close(sockfd); // child doesn't need the listener
char input[20];
char *pointer;
printf("Type in an server's input: ");
scanf("%s", input);
pointer = input; //Will need to clean this up to be more effcient... later
if (send(new_fd, pointer, strlen(input), 0) == -1) //Need to change the length to
//the actual length of the
//input... later.
perror("send");
close(new_fd);
exit(0);
}
char Cinput[20];
if ((recv(new_fd, Cinput, strlen(Cinput), 0)) == 0) { //NEW LINE ADDED HERE
printf("No more messages");
}
if ((recv(new_fd, Cinput, strlen(Cinput), 0)) == -1) {
perror("recv");
exit(1);
}
printf("Server: received '%s'\n",Cinput);
close(new_fd); // Parent doesn't need this
}
return 0;
}
客户端.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define PORT "3490" // The port client will be connecting to
#define MAXDATASIZE 100 // Max number of bytes we can get at once
// Get sockaddr, IPv4 or IPv6:
void *get_in_addr(struct sockaddr *sa)
{
if (sa->sa_family == AF_INET) {
return &(((struct sockaddr_in*)sa)->sin_addr);
}
return &(((struct sockaddr_in6*)sa)->sin6_addr);
}
int main(int argc, char *argv[])
{
int sockfd, numbytes;
char buf[MAXDATASIZE];
struct addrinfo hints, *servinfo, *p;
/*
This is what is in the struct
struct addrinfo {
int ai_flags; // AI_PASSIVE, AI_CANONNAME, etc.
int ai_family; // AF_INET, AF_INET6, AF_UNSPEC
int ai_socktype; // SOCK_STREAM, SOCK_DGRAM
int ai_protocol; // Use 0 for "any"
size_t ai_addrlen; // Size of ai_addr in bytes
struct sockaddr *ai_addr; // struct sockaddr_in or _in6
char *ai_canonname; // Full canonical hostname
struct addrinfo *ai_next; // Linked list, next node
};
getaddrinfo() will return a pointer to this
*/
int rv;
char s[INET6_ADDRSTRLEN];
if (argc != 2) {
fprintf(stderr,"usage: client hostname\n");
exit(1);
}
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
// Loop through all the results and connect to the first we can
for(p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype,
p->ai_protocol)) == -1) {
perror("client: socket");
continue;
}
if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
close(sockfd);
perror("client: connect");
continue;
}
break;
}
if (p == NULL) {
fprintf(stderr, "client: failed to connect\n");
return 2;
}
inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr),
s, sizeof s);
printf("client: connecting to %s\n", s);
freeaddrinfo(servinfo); // All done with this structure
while(1)//NEW LINE ADDEDthis is getting the client to repeat asking for the input, but doesn't send it.
{
if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == 0) { //NEW LINE ADDED
printf("Shutdown");
}
if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {
perror("recv");
exit(1);
}
buf[numbytes] = '\0';
printf("client: received '%s'\n",buf);
char Cinput[20];
char *pointer;
printf("Type in an client's input: ");
scanf("%s", Cinput);
pointer = Cinput;
if (send(sockfd, pointer, strlen(Cinput), 0) == -1)
{
perror("send");
close(sockfd);
exit(0);
}
}
close(sockfd); //As soon as the client receives a message, it closes the socket.
//We probably need a while loop in here in order to keep the socket open,
//but what are the parameters for the while loop?
return 0;
}
下面的伪代码将确保同一个客户端和服务器可以无限地向对方发送消息，直到其中一个挂断：
socket.connect到它。recv数据。recv返回0，则表示另一端已执行有序关闭。转到步骤 7。send回复。socket.bind套接字到一个地址。listening。accept一个连接。send数据。recv回复。recv返回0，则表示另一端已执行有序关闭。转至步骤 4 接受新连接。