Piye cara Docker networking lan port mapping ngreti?

Question

Accepted Answer

Docker nyediakne **networking** supaya container bisa komunikasi karo siji lan sijine lan karo bab nang luar. **Port mapping** mbukak port container menyang host, lan **networks** nglegani container ngobrol karo siji lan sijine nganggo asma. Ngerti dasare penting banget kanggo jalanke aplikasi sing konektif.

## Port mapping — bukak container menyang host

```bash
# -p HOST_PORT:CONTAINER_PORT maps a host port to a container port
docker run -p 8080:80 nginx
# → nginx listens on port 80 INSIDE the container;
#   accessing localhost:8080 on the HOST reaches it
# → without -p, the container's ports aren't accessible from outside
```

**Port mapping** (`-p host:container`) nggawe port internal container bisa ditengo saka host — perlu kanggo akses aplikasi web ing container, API, dll. saka njaba container.

## Komunikasi container menyang container (user-defined networks)

```bash
# create a network; containers on it can reach each other BY NAME
docker network create mynet
docker run -d --name db --network mynet postgres
docker run -d --name api --network mynet myapi
# → the "api" container can connect to the database at hostname "db" (Docker DNS)
#   e.g. DATABASE_URL=postgres://db:5432/...
```

Sang **user-defined network**, container bisa tengo siji lan sijine kanthi **asma container** (Docker nyediakne DNS resolution) — dadi aplikasi container konek menyang database container nganggo asma dadi hostname, ora perlu IP address.

## Tipe network

```text
bridge   → the default; containers on a bridge network communicate; isolated from host
           (user-defined bridge networks add name-based DNS — preferred)
host     → the container shares the host's network directly (no isolation, no mapping)
none     → no networking
overlay  → spans multiple hosts (for Docker Swarm / multi-host clusters)
```

## Dene penting banget

Ngerti Docker networking lan port mapping penting banget kanggo jalanke aplikasi nyata sing konektif ing Docker, dadi pengetahuan praktikal penting. **Port mapping** (`-p host:container`) dadi dhasar lan dienggo terus-terusan — tanpa iki, aplikasi web ing container utawa API ora bisa diakses saka njaba container, dadi ngerti carane bukak port container menyang host perlu banget kanggo bener-bener nganggo layanan ing container.

Ko penting kuwi **komunikasi container menyang container**: ngerti yen sang **user-defined network**, container bisa tengo siji lan sijine **kanthi asma** (nganggo DNS bawahan Docker) penting banget kanggo aplikasi multi-container — aplikasi container konek menyang database container nganggo asma container minangka hostname (cth. `postgres://db:5432`) iku pola umum banget, lan ngerti iki perlu kanggo nggawe aplikasi sing ana ing multi-container (app + database + cache, dll.).

Ngerti **tipe network** (bridge minangka default karo user-defined bridges nambah DNS berbasis asma, host kanggo bareng network host, overlay kanggo cluster multi-host) ngasih konteks kanggo konfigurasi networking kanthi bener.

Karena aplikasi nyata involve layanan sing komunikasi (aplikasi web tengo database, layanan manggilan siji lan sijine) lan diakses saka njaba (port sing dibukak), lan karena Docker networking (port mapping kanggo akses eksternal, komunikasi named container sang networks) iku carane konektivitas iki bisa gawekne, ngerti dhasar Docker networking iku pengetahuan penting lan sering dienggo kanggo jalanke aplikasi containerized sing konektif — perlu kanggo apa-apa saliyane container terisolasi siji, lan skill dhasar kanggo aplikasi multi-container sing iku norma ing Docker usage nyata.