socket进程通信与网络通信使用的是统一套接口，只是地址结构与某些参数不同。
一。创建socket服务端的流程如下：
（1）创建socket，类型为AF_LOCAL或AF_UNIX，表示用于进程通信：
[cpp]
view plaincopyint server_fd;
int client_fd;//client file descriptor
struct sockaddr_un server_addr;
struct sockaddr_un client_addr;
size_t server_len,client_len;
//cteate server socket
//delete old socket file
unlink(SERVER_NAME);
if ((server_fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
perror("socket");
exit(1);
}
(2)命名socket。这里面有一个很关键的东西，socket进程通信命名方式有两种。一是普通的命名，socket会根据此命名创建一个同名的socket文件，客户端连接的时候通过读取该socket文件连接到socket服务端。这种方式的弊端是服务端必须对socket文件的路径具备写权限，客户端必须知道socket文件路径，且必须对该路径有读权限。另外一种命名方式是抽象命名空间，这种方式不需要创建socket文件，只需要命名一个全局名字，即可让客户端根据此名字进行连接。后者的实现过程与前者的差别是，后者在对地址结构成员sun_path数组赋值的时候，必须把第一个字节置0，即sun_path[0] = 0，下面用代码说明：
第一种方式：
[cpp]
view plaincopy//name the server socket
server_addr.sun_family = AF_UNIX;
strcpy(server_addr.sun_path,SERVER_NAME);
server_len = sizeof(struct sockaddr_un);
client_len = server_len;
第二种方式：
[cpp]
view plaincopy//name the socket
server_addr.sun_family = AF_UNIX;
strcpy(server_addr.sun_path, SERVER_NAME);
server_addr.sun_path[0]=0;
//server_len = sizeof(server_addr);
server_len = strlen(SERVER_NAME) + offsetof(struct sockaddr_un, sun_path);
其中，offsetof函数在#include <stddef.h>头文件中定义。因第二种方式的首字节置0，我们可以在命名字符串SERVER_NAME前添加一个占位字符串，例如:
[cpp]
view plaincopy#define SERVER_NAME @socket_server
前面的@符号就表示占位符，不算为实际名称。
或者可以把第二种方式的实现封装成一个函数：
[cpp]
view plaincopyint makeAddr(const char* name, struct sockaddr_un* pAddr, socklen_t* pSockLen)
{
int nameLen = strlen(name);
if (nameLen >= (int) sizeof(pAddr->sun_path) -1) /* too long? */
return -1;
pAddr->sun_path[0] = '\0'; /* abstract namespace */
strcpy(pAddr->sun_path+1, name);
pAddr->sun_family = AF_UNIX;
*pSockLen = 1 + nameLen + offsetof(struct sockaddr_un, sun_path);
return 0;
}
像下面这样使用这个函数：
[cpp]
view plaincopymakeAddr("server_socket", &server_addr, &server_len);
提示：客户端连接服务器的时候，必须与服务端的命名方式相同，即如果服务端是普通命名方式，客户端的地址也必须是普通命名方式；如果服务端是抽象命名方式，客户端的地址也必须是抽象命名方式。
（3）绑定并侦听
[cpp]
view plaincopybind(server_sockfd, (struct sockaddr *)&server_addr, server_len);
//listen the server
listen(server_sockfd, 5);
（4）等待客户端连接，并读写数据。
[cpp]
view plaincopywhile(1){
printf("server waiting...\n");
//accept client connect
client_len = sizeof(client_addr);
client_sockfd = accept(server_sockfd,(struct sockaddr*)&client_addr, &client_len);
//read data from client socket
read(client_sockfd, &ch, 1);
printf("read from client %d: %c",client_sockfd,ch);
ch ++;
write(client_sockfd, &ch, 1);
close(client_sockfd);
usleep(100);//1000 miliseconds = 1 second
}
二 socket客户端创建流程
（1）创建socket
（2）命名socket
（3）连接到服务端：
[cpp]
view plaincopy//connect to server
result = connect(sockfd, (struct sockaddr*)&address, len);
（4）与服务端进行通信
[cpp]
view plaincopy//communicate with server socket
while(1)
{
printf("set send content:");
scanf("%c",&ch);
write(sockfd, &ch, 1);
printf("send to server:%c \n",ch);
read(sockfd, &ch, 1);
printf("read from server: %c\n", ch);
}
完整代码如下：
（1）服务端server.c：
[cpp]
view plaincopy#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<sys/un.h>
#include<unistd.h>
#include<stdlib.h>
#include <stddef.h>
#define SERVER_NAME "@server_socket"
/*
* Create a UNIX-domain socket address in the Linux "abstract namespace".
*
* The socket code doesn't require null termination on the filename, but
* we do it anyway so string functions work.
*/
int makeAddr(const char* name, struct sockaddr_un* pAddr, socklen_t* pSockLen)
{
int nameLen = strlen(name);
if (nameLen >= (int) sizeof(pAddr->sun_path) -1) /* too long? */
return -1;
pAddr->sun_path[0] = '\0'; /* abstract namespace */
strcpy(pAddr->sun_path+1, name);
pAddr->sun_family = AF_UNIX;
*pSockLen = 1 + nameLen + offsetof(struct sockaddr_un, sun_path);
return 0;
}
int main()
{
int server_sockfd, client_sockfd;
socklen_t server_len, client_len;
struct sockaddr_un server_addr;
struct sockaddr_un client_addr;
char ch;
int nread;
//delete the old server socket
//unlink("server_socket");
//create socket
server_sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
//name the socket
server_addr.sun_family = AF_UNIX;
strcpy(server_addr.sun_path, SERVER_NAME);
server_addr.sun_path[0]=0;
//server_len = sizeof(server_addr);
server_len = strlen(SERVER_NAME) + offsetof(struct sockaddr_un, sun_path);
//makeAddr("server_socket", &server_addr, &server_len);
bind(server_sockfd, (struct sockaddr *)&server_addr, server_len);
//listen the server
listen(server_sockfd, 5);
client_sockfd = -1;
client_len = sizeof(client_addr);
while(1){
printf("server waiting...\n");
//accept client connect
if(client_sockfd == -1){
client_sockfd = accept(server_sockfd,(struct sockaddr*)&client_addr, &client_len);
}
//read data from client socket
nread = read(client_sockfd, &ch, 1);
if(nread == 0){//client disconnected
printf("client %d disconnected\n",client_sockfd);
client_sockfd = -1;
}
else{
printf("read from client %d: %c\n",client_sockfd,ch);
ch ++;
write(client_sockfd, &ch, 1);
}
usleep(100);//1000 miliseconds = 1 second
}
return 0;
}
（2）客户端client.c
[cpp]
view plaincopy#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<sys/un.h>
#include<unistd.h>
#include<stdlib.h>
#include <stddef.h>
#define SERVER_NAME "@server_socket"
/*
* Create a UNIX-domain socket address in the Linux "abstract namespace".
*
* The socket code doesn't require null termination on the filename, but
* we do it anyway so string functions work.
*/
int makeAddr(const char* name, struct sockaddr_un* pAddr, socklen_t* pSockLen)
{
int nameLen = strlen(name);
if (nameLen >= (int) sizeof(pAddr->sun_path) -1) /* too long? */
return -1;
pAddr->sun_path[0] = '\0'; /* abstract namespace */
strcpy(pAddr->sun_path+1, name);
pAddr->sun_family = AF_UNIX;
*pSockLen = 1 + nameLen + offsetof(struct sockaddr_un, sun_path);
return 0;
}
int main()
{
int sockfd;
socklen_t len;
struct sockaddr_un address;
int result;
char ch = 'A';
//create socket
sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
//name the server socket
//makeAddr("server_socket", &address, &len);
address.sun_family = AF_UNIX;
strcpy(address.sun_path, SERVER_NAME);
address.sun_path[0]=0;
//len = sizeof(address);
len = strlen(SERVER_NAME) + offsetof(struct sockaddr_un, sun_path);
//connect to server
result = connect(sockfd, (struct sockaddr*)&address, len);
if(result == -1)
{
perror("opps:client1");
exit(1);
}
//communicate with server socket
while(1)
{
printf("set send content:");
scanf("%c",&ch);
write(sockfd, &ch, 1);
printf("send to server:%c \n",ch);
read(sockfd, &ch, 1);
printf("read from server: %c\n", ch);
}
exit(0);
}
