C语言socket编程实例

文章目录

- - 一、实验说明
  - 二、面向连接的流式套接字 C/S 例子
  - 三、非阻塞的多人聊天服务器端例子
  - 四、简单的 IPv6 UDP socket编程
  - 四、参考书籍和??

一、实验说明

服务端：树莓派(可以使用putty、xshell、vnc远程操作树莓派，这里使用vnc)
客户端：Ubuntu
所用语言：C语言
树莓派和Ubuntu应处于同一个局域网下(可以用手机热点连接)

二、面向连接的流式套接字 C/S 例子

在树莓派下，新建一个 Server1.c，命令 nano Server1.c，然后写入如下内容

#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 "9090" // the port users will be connecting to
#define BACKLOG 10
// how many pending connections queue will hold
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");
while(1) { // main accept() loop
sin_size = sizeof their_addr;
new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
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
if (send(new_fd, "Hello, world!", 13, 0) == -1)
perror("send");
close(new_fd);
exit(0);
}
close(new_fd); // parent doesn't need this
}
return 0;
}

然后编译并运行

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gcc Server1.c -o Server1
./Server1

在Ubuntu系统下，新建一个Client1.c文件，命令gedit Client1.c，然后写入如下内容

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#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 "9090" //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;
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
if((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1)
{
perror("recv");
exit(1);
}
buf[numbytes] = '\0';
printf("client:received %s\n",buf);
close(sockfd);
return 0;
}

然后编译并运行

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gcc Client1.c -o Client1
./Client1 192.168.43.161

注意：这里后面跟的IP是自己服务端的IP，即，自己树莓派的IP
运行结果如下

三、非阻塞的多人聊天服务器端例子

在树莓派下，新建一个Server2.c文件，命令nano Server2.c，然后写入如下内容

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

#define PORT "9090" //port we're listening on

//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)
{
fd_set master;
// master file descriptor list
fd_set read_fds; // temp file descriptor list for select()
int fdmax;
// maximum file descriptor number
int listener;
// listening socket descriptor
int newfd;
// newly accept()ed socket descriptor
struct sockaddr_storage remoteaddr; // client address
socklen_t addrlen;
char buf[256];
// buffer for client data
int nbytes;
char remoteIP[INET6_ADDRSTRLEN];
int yes=1;
// for setsockopt() SO_REUSEADDR, below
int i, j, rv;
struct addrinfo hints, *ai, *p;
FD_ZERO(&master);
// clear the master and temp sets
FD_ZERO(&read_fds);
// get us a socket and bind it
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
if((rv = getaddrinfo(NULL, PORT, &hints, &ai)) != 0)
{
fprintf(stderr, "selectserver:%s\n", gai_strerror(rv));
exit(1);
}

for(p = ai; p != NULL; p = p->ai_next)
{
listener = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
if(listener < 0)
{
continue;
}
// lose the pesky "address already in use" error message
setsockopt(listener, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
if(bind(listener, p->ai_addr, p->ai_addrlen) < 0)
{
close(listener);
continue;
}
break;
}
// if we got here, it means we didn't get bound
if(p == NULL)
{
fprintf(stderr, "selectserver:failed to bind\n");
exit(2);
}

freeaddrinfo(ai); // all done with this
// listen
if(listen(listener, 10) == -1)
{
perror("listen");
exit(3);
}
// add the listener to the master set
FD_SET(listener, &master);
// keep track of the biggest file descriptor
fdmax = listener; // so far, it's this one
// main loop
for(;;)
{
read_fds = master; // copy it
if(select(fdmax + 1, &read_fds, NULL, NULL, NULL) == -1)
{
perror("select");
exit(4);
}
// run through the existing connections looking for data to read
for(i = 0; i <= fdmax; i++)
{
if(FD_ISSET(i, &read_fds))// we got one!!
{
if(i == listener)
{
// handle new connections
addrlen = sizeof remoteaddr;
newfd = accept(listener, (struct sockaddr *)&remoteaddr, &addrlen);

if(newfd == -1)
{
perror("accept");
}
else
{
FD_SET(newfd, &master); // add to master set
if(newfd > fdmax)
{
// keep track of the max
fdmax = newfd;
}
printf("selectserver: new connection from %s on "
"socket %d\n",
inet_ntop(remoteaddr.ss_family,
get_in_addr((struct sockaddr*)&remoteaddr),
remoteIP, INET6_ADDRSTRLEN),
newfd);
}
}
else
{
// handle data from a client
if((nbytes = recv(i, buf, sizeof buf, 0)) <= 0)
{
// got error or connection closed by client
if(nbytes == 0)
{
// connection closed
printf("selectserver:socket %d hung up\n", i);
}
else
{
perror("recv");
}
close(i);// bye!
FD_CLR(i, &master);// remove from master set
}
else
{
// we got some data from a client
for(j =0; j <= fdmax; j++)
{
// send to everyone!
if(FD_ISSET(j, &master))
{
// except the listener and ourselves
if(j != listener && j != i)
{
if(send(j, buf, nbytes, 0) == -1)
{
perror("send");
}
}
}
}
}
} //END handle from client
} //END got new incoming connection
} //END looping through file descriptors
} //END for(;;)--and you thought it would never end!
return 0;
}

编译并运行

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gcc Server2.c -o Server2
./Server2

在Ubuntu下新建一个Client2.c文件，命令gedit Client2.c，然后写入如下内容

#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 "9090" //the port client will be connecting to
#define MAXDATASIZE 100 //max number of bytes we can get at once

int sockfd, numbytes;
char buf[MAXDATASIZE];

//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);
}

void *recvMag()
{
while(1)
{
if((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1)
{
perror("recv");
exit(1);
}
if(numbytes == 1)
continue;
buf[numbytes] = '\0';
printf("\nreceived：%s\n",buf);
}
}

int main(int argc, char *argv[])
{
//int sockfd, numbytes;
//char buf[MAXDATASIZE];
struct addrinfo hints, *servinfo, *p;
int rv;
char s[INET6_ADDRSTRLEN];
pthread_t t1;
char mag[MAXDATASIZE];

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

int err = pthread_create(&t1, NULL, recvMag, NULL);
if(err != 0)
{
printf("receive failed");
exit(1);
}

while(1)
{
scanf("%s", mag);
if(send(sockfd, mag, sizeof mag, 0) == -1)
{
printf("send failed!\n");
}
}
return 0;
}

注意：因为是一个多人聊天程序，所以这里至少应该有两个客户端，本人是重新再开个Ubuntu的虚拟机，重复客户端的操作

编译并运行

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gcc -pthread Client2.c -o Client2
./Client2 192.168.43.161
运行结果如下

① 客户端

② 服务端

四、简单的 IPv6 UDP socket编程

在树莓派和Ubuntu下查看自己的IPv6地址地址，ifconfig，然后再看双方能不能ping通

在树莓派下新建一个Server4.c文件，命令nano Server4.c，然后写入如下内容

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#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
struct sockaddr_in6 s_addr;
struct sockaddr_in6 c_addr;
int sock;
socklen_t addr_len;
int len;
char buff[128];
char buf_ip[128];

if ((sock = socket(AF_INET6, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(errno);
} else
printf("create socket.\n\r");

memset(&s_addr, 0, sizeof(struct sockaddr_in6));
s_addr.sin6_family = AF_INET6;

if (argv[2])
s_addr.sin6_port = htons(atoi(argv[2]));
else
s_addr.sin6_port = htons(4444);

if (argv[1])
inet_pton(AF_INET6, argv[1], &s_addr.sin6_addr);
else
s_addr.sin6_addr = in6addr_any;

if ((bind(sock, (struct sockaddr *) &s_addr, sizeof(s_addr))) == -1) {
perror("bind");
exit(errno);
} else
printf("bind address to socket.\n\r");

addr_len = sizeof(c_addr);
while (1) {
len = recvfrom(sock, buff, sizeof(buff) - 1, 0,
(struct sockaddr *) &c_addr, &addr_len);
if (len < 0) {
perror("recvfrom");
exit(errno);
}

buff[len] = '\0';
printf("receive from %s: buffer:%s\n\r",
inet_ntop(AF_INET6, &c_addr.sin6_addr, buf_ip, sizeof(buf_ip)),
buff);
}
return 0;
}

编译运行

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gcc Server4.c -o server4
./server4 2409:8960:1e48:f1a:b6a4:81d5:7021:4873 9090

再Ubuntu下，新建一个Client4.c文件，然后写入如下内容

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#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
struct sockaddr_in6 s_addr;
int sock;
int addr_len;
int len;
char buff[128];

if ((sock = socket(AF_INET6, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(errno);
} else
printf("create socket.\n\r");

s_addr.sin6_family = AF_INET6;
if (argv[2])
s_addr.sin6_port = htons(atoi(argv[2]));
else
s_addr.sin6_port = htons(4444);

if (argv[1])
inet_pton(AF_INET6, argv[1], &s_addr.sin6_addr);
else {
printf("usage:./command ip port\n");
exit(0);
}

addr_len = sizeof(s_addr);
strcpy(buff, "hello i'm here");
len = sendto(sock, buff, strlen(buff), 0,
(struct sockaddr *) &s_addr, addr_len);
if (len < 0) {
printf("\n\rsend error.\n\r");
return 3;
}

printf("send success.\n\r");
return 0;
}

编译运行

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gcc Client4.c -o Client4
./Client4 2409:8960:1e48:f1a:b6a4:81d5:7021:4873 9090
运行结果如下

① 客户端

② 服务端
wireshark抓包

四、参考书籍和??

Ubuntu 与树莓派之间的两个 socket 应用实例：C/S 和多人聊天
《网络编程技术》
简单的IPv6 UDP/TCP socket编程 – 两台Linux实现简单的ipv6通信